<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019b2283-d8ad-7804-b1fc-3e4fd38b6eff,g:f9f69a52-fb6a-4a9b-917d-c857ae4ac04e-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.biogenidec.com/role/ConsolidatedStatementsofIncome" xlink:type="simple" xlink:href="biib-20251231.xsd#ConsolidatedStatementsofIncome"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/ConsolidatedStatementsofIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostsAndExpenses"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019b2283-dc37-7b11-acb7-64fb361a4fb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019b2283-dc37-7b11-acb7-64fb361a4fb8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_019b2283-dc37-7e65-8d63-7bfcfa60552d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_019b2283-dc37-7e65-8d63-7bfcfa60552d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019b2283-dc37-71d5-88cb-d4d40c461c95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019b2283-dc37-71d5-88cb-d4d40c461c95" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_AmortizationAndImpairmentOfAcquiredIntangibleAssets_019b2283-dc37-7320-9ed9-883ec4f7b69b" xlink:href="biib-20251231.xsd#biib_AmortizationAndImpairmentOfAcquiredIntangibleAssets"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_biib_AmortizationAndImpairmentOfAcquiredIntangibleAssets_019b2283-dc37-7320-9ed9-883ec4f7b69b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfIntangibleAssets_019b2283-dc37-7ea0-8946-121448efb231" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDispositionOfIntangibleAssets"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_us-gaap_GainLossOnDispositionOfIntangibleAssets_019b2283-dc37-7ea0-8946-121448efb231" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_CollaborationProfitLossSharing_019b2283-dc37-75b5-a70d-6039d68965f9" xlink:href="biib-20251231.xsd#biib_CollaborationProfitLossSharing"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_biib_CollaborationProfitLossSharing_019b2283-dc37-75b5-a70d-6039d68965f9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_019b2283-dc37-74a9-b319-b850507e3f7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_019b2283-dc37-74a9-b319-b850507e3f7b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019b2283-dc37-7817-8180-6922bd2e9d71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019b2283-dc37-7817-8180-6922bd2e9d71" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_019b2283-dc37-7410-8600-352f98514249" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringCharges"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_us-gaap_RestructuringCharges_019b2283-dc37-7410-8600-352f98514249" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_ResearchAndDevelopmentExpenseAcquiredInProcessCost_019b22d1-aace-7b6e-a9b6-3667de987fdf" xlink:href="biib-20251231.xsd#biib_ResearchAndDevelopmentExpenseAcquiredInProcessCost"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_biib_ResearchAndDevelopmentExpenseAcquiredInProcessCost_019b22d1-aace-7b6e-a9b6-3667de987fdf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseImpairmentLoss_019bc2d6-9fd4-7d9d-82aa-9ddbc97f3bf0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseImpairmentLoss"/>
    <link:calculationArc order="11" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_019b2283-dc37-7948-8276-36bfbf1f15db" xlink:to="loc_us-gaap_OperatingLeaseImpairmentLoss_019bc2d6-9fd4-7d9d-82aa-9ddbc97f3bf0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019b2283-dc37-710e-9a7d-ff7f4d90692d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2283-dc37-7f21-9e36-df622d5b4adc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019b2283-dc37-710e-9a7d-ff7f4d90692d" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2283-dc37-7f21-9e36-df622d5b4adc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019b2283-dc37-7d81-9d14-a1b3224eb505" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019b2283-dc37-710e-9a7d-ff7f4d90692d" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019b2283-dc37-7d81-9d14-a1b3224eb505" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019b2283-dc37-7acf-9b53-c99fb52eaaf5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019b2283-dc37-7000-954c-b96007b9e0b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-dc37-7acf-9b53-c99fb52eaaf5" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019b2283-dc37-7000-954c-b96007b9e0b8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019b2283-dc37-77ef-b770-eaf1dd76620a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-dc37-7acf-9b53-c99fb52eaaf5" xlink:to="loc_us-gaap_ProfitLoss_019b2283-dc37-77ef-b770-eaf1dd76620a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2283-dc37-7df9-b78f-535713807ef0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019b2283-dc37-7416-b41f-76998d9bd0a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2283-dc37-7df9-b78f-535713807ef0" xlink:to="loc_us-gaap_Revenues_019b2283-dc37-7416-b41f-76998d9bd0a4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019b2283-dc37-744a-9b48-9de7e4552e21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostsAndExpenses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2283-dc37-7df9-b78f-535713807ef0" xlink:to="loc_us-gaap_CostsAndExpenses_019b2283-dc37-744a-9b48-9de7e4552e21" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/ConsolidatedStatementsofComprehensiveIncome" xlink:type="simple" xlink:href="biib-20251231.xsd#ConsolidatedStatementsofComprehensiveIncome"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/ConsolidatedStatementsofComprehensiveIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2283-dcf3-71f3-9dff-8d9a11ba6aaa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_019b2283-dcf3-73b5-8259-dc7692b29d55" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2283-dcf3-71f3-9dff-8d9a11ba6aaa" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_019b2283-dcf3-73b5-8259-dc7692b29d55" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent_019b2283-dcf3-7185-8d69-8b5005324515" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2283-dcf3-71f3-9dff-8d9a11ba6aaa" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent_019b2283-dcf3-7185-8d69-8b5005324515" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_019b2283-dcf3-7606-a952-a99800fff2d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2283-dcf3-71f3-9dff-8d9a11ba6aaa" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_019b2283-dcf3-7606-a952-a99800fff2d8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_019b2283-dcf3-7c70-9891-25a1d897d2bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2283-dcf3-71f3-9dff-8d9a11ba6aaa" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_019b2283-dcf3-7c70-9891-25a1d897d2bd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019b2283-dcf3-77e0-ada7-cba43d49ba38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_019b2283-dcf3-720d-a56a-999afeb5c8b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_019b2283-dcf3-77e0-ada7-cba43d49ba38" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_019b2283-dcf3-720d-a56a-999afeb5c8b5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-794f-88b0-54efedca8bc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_019b2283-dcf3-77e0-ada7-cba43d49ba38" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-794f-88b0-54efedca8bc7" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/ConsolidatedStatementsofComprehensiveIncome_1" xlink:type="simple" xlink:href="biib-20251231.xsd#ConsolidatedStatementsofComprehensiveIncome_1"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/ConsolidatedStatementsofComprehensiveIncome_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019b2283-dcf3-7098-9716-bd2de3d88d7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2283-dcf3-7194-a996-96ef733fd53b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_019b2283-dcf3-7098-9716-bd2de3d88d7f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2283-dcf3-7194-a996-96ef733fd53b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019b2283-dcf3-7955-b001-33487082faff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_019b2283-dcf3-7098-9716-bd2de3d88d7f" xlink:to="loc_us-gaap_NetIncomeLoss_019b2283-dcf3-7955-b001-33487082faff" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="biib-20251231.xsd#ConsolidatedBalanceSheets"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019b2283-dcf3-7c4a-9071-bf4336b66f1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_019b2283-dcf3-7873-a256-2f4d7a009175" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNet"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2283-dcf3-7c4a-9071-bf4336b66f1c" xlink:to="loc_us-gaap_InventoryNet_019b2283-dcf3-7873-a256-2f4d7a009175" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019b2283-dcf3-77e0-be4b-30bd13068ece" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2283-dcf3-7c4a-9071-bf4336b66f1c" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019b2283-dcf3-77e0-be4b-30bd13068ece" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019b2283-dcf3-7c86-9af9-0e5c22370dc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2283-dcf3-7c4a-9071-bf4336b66f1c" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_019b2283-dcf3-7c86-9af9-0e5c22370dc2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_DueFromUnconsolidatedJointBusiness_019b2283-dcf3-7ba3-98eb-06c4e6bbce14" xlink:href="biib-20251231.xsd#biib_DueFromUnconsolidatedJointBusiness"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2283-dcf3-7c4a-9071-bf4336b66f1c" xlink:to="loc_biib_DueFromUnconsolidatedJointBusiness_019b2283-dcf3-7ba3-98eb-06c4e6bbce14" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_019b2283-dcf3-7ac0-8ca6-d87f70704d69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2283-dcf3-7c4a-9071-bf4336b66f1c" xlink:to="loc_us-gaap_OtherAssetsCurrent_019b2283-dcf3-7ac0-8ca6-d87f70704d69" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_019c055b-155d-799e-a796-682b7ff58bb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2283-dcf3-7c4a-9071-bf4336b66f1c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_019c055b-155d-799e-a796-682b7ff58bb2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7dc0-ab1c-b5b471a4d3be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019b2283-dcf3-73c8-8eba-94fac9462bfe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7dc0-ab1c-b5b471a4d3be" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019b2283-dcf3-73c8-8eba-94fac9462bfe" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_019b2283-dcf3-7d19-abc9-c18acc7ee63f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValue"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7dc0-ab1c-b5b471a4d3be" xlink:to="loc_us-gaap_TreasuryStockValue_019b2283-dcf3-7d19-abc9-c18acc7ee63f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValueOutstanding_019b2283-dcf3-7f79-8bd8-b238ae0ca8a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockValueOutstanding"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7dc0-ab1c-b5b471a4d3be" xlink:to="loc_us-gaap_PreferredStockValueOutstanding_019b2283-dcf3-7f79-8bd8-b238ae0ca8a6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019b2283-dcf3-7298-9719-34307530a126" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7dc0-ab1c-b5b471a4d3be" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019b2283-dcf3-7298-9719-34307530a126" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019b2283-dcf3-7c7f-b823-81d6a8ed77a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7dc0-ab1c-b5b471a4d3be" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019b2283-dcf3-7c7f-b823-81d6a8ed77a4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValueOutstanding_019b2283-dcf3-7d3d-af53-2e2b2542c23e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValueOutstanding"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7dc0-ab1c-b5b471a4d3be" xlink:to="loc_us-gaap_CommonStockValueOutstanding_019b2283-dcf3-7d3d-af53-2e2b2542c23e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019b2283-dcf3-7006-9816-6b7bcd6b13de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019b2283-dcf3-759e-a842-41a0180499fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2283-dcf3-7006-9816-6b7bcd6b13de" xlink:to="loc_us-gaap_LiabilitiesCurrent_019b2283-dcf3-759e-a842-41a0180499fe" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermNotesPayable_019b2283-dcf3-7a12-a7d0-16ca983d24dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermNotesPayable"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2283-dcf3-7006-9816-6b7bcd6b13de" xlink:to="loc_us-gaap_LongTermNotesPayable_019b2283-dcf3-7a12-a7d0-16ca983d24dd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019b2283-dcf3-79fd-b950-60330172bb11" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2283-dcf3-7006-9816-6b7bcd6b13de" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019b2283-dcf3-79fd-b950-60330172bb11" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019b2283-dcf3-7657-a6c0-20cfbb225e18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2283-dcf3-7006-9816-6b7bcd6b13de" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019b2283-dcf3-7657-a6c0-20cfbb225e18" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_019b2283-dcf3-7faa-a8a6-6e932d81ec88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2283-dcf3-7006-9816-6b7bcd6b13de" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_019b2283-dcf3-7faa-a8a6-6e932d81ec88" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019b2283-dcf3-7eff-b541-56cc3f9c6353" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7c8c-91de-3633bdc654b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019b2283-dcf3-7eff-b541-56cc3f9c6353" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2283-dcf3-7c8c-91de-3633bdc654b7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019b2283-dcf3-765b-b70a-2239c45ac1b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019b2283-dcf3-7eff-b541-56cc3f9c6353" xlink:to="loc_us-gaap_Liabilities_019b2283-dcf3-765b-b70a-2239c45ac1b9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019b2283-dcf3-7752-bd98-6887411af998" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019b2283-dcf3-7eff-b541-56cc3f9c6353" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019b2283-dcf3-7752-bd98-6887411af998" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019b2283-dcf3-74fc-9cc8-b242212ae0af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019b2283-dcf3-759c-a337-9308e0b24846" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2283-dcf3-74fc-9cc8-b242212ae0af" xlink:to="loc_us-gaap_AccountsPayableCurrent_019b2283-dcf3-759c-a337-9308e0b24846" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxesPayableCurrent_019b2283-dcf3-7ab6-afb2-3595d2438785" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxesPayableCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2283-dcf3-74fc-9cc8-b242212ae0af" xlink:to="loc_us-gaap_TaxesPayableCurrent_019b2283-dcf3-7ab6-afb2-3595d2438785" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-dcf3-7468-bf50-15887e528882" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2283-dcf3-74fc-9cc8-b242212ae0af" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-dcf3-7468-bf50-15887e528882" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_019b2283-dcf3-7961-8a8e-c8cf7f1ab36d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2283-dcf3-74fc-9cc8-b242212ae0af" xlink:to="loc_us-gaap_DebtCurrent_019b2283-dcf3-7961-8a8e-c8cf7f1ab36d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019b2283-dcf3-72bd-bef9-2840e0553a00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:to="loc_us-gaap_AssetsCurrent_019b2283-dcf3-72bd-bef9-2840e0553a00" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019b2283-dcf3-7d0e-a1a3-a44cdcf8b8c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019b2283-dcf3-7d0e-a1a3-a44cdcf8b8c7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019b2283-dcf3-7951-bdcd-860648bb3268" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019b2283-dcf3-7951-bdcd-860648bb3268" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b2283-dcf3-724b-a066-92fbd0c41799" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b2283-dcf3-724b-a066-92fbd0c41799" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019b2283-dcf3-70e5-8fa3-449e37ab5791" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:to="loc_us-gaap_Goodwill_019b2283-dcf3-70e5-8fa3-449e37ab5791" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_019b2283-dcf3-71f3-8381-8005dc80d19d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_019b2283-dcf3-71f3-8381-8005dc80d19d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019b2283-dcf3-797a-bc77-bb0684238123" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_019b2283-dcf3-797a-bc77-bb0684238123" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_019beba5-77c3-728c-95dd-d5ee0b81d377" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2283-dcf3-7c83-8ead-14fb063675d4" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_019beba5-77c3-728c-95dd-d5ee0b81d377" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/ConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="biib-20251231.xsd#ConsolidatedStatementsofCashFlows"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/ConsolidatedStatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b99a7-b961-7bca-9c22-bb298b12a75a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_019b99a7-b961-7e98-a740-20152706ae0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b99a7-b961-7bca-9c22-bb298b12a75a" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_019b99a7-b961-7e98-a740-20152706ae0b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019b99a7-b961-7650-b18e-a3657e815162" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b99a7-b961-7bca-9c22-bb298b12a75a" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019b99a7-b961-7650-b18e-a3657e815162" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_019b99a7-b961-7cf6-975f-4f31d02ca8cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b99a7-b961-7bca-9c22-bb298b12a75a" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_019b99a7-b961-7cf6-975f-4f31d02ca8cd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsToMinorityShareholders_019b99a7-b961-7f86-bae1-2bb462ab73ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromPaymentsToMinorityShareholders"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b99a7-b961-7bca-9c22-bb298b12a75a" xlink:to="loc_us-gaap_ProceedsFromPaymentsToMinorityShareholders_019b99a7-b961-7f86-bae1-2bb462ab73ec" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities_019b99a7-b961-7597-b610-68e0daef9ce7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b99a7-b961-7bca-9c22-bb298b12a75a" xlink:to="loc_us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities_019b99a7-b961-7597-b610-68e0daef9ce7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019b99a7-b961-7150-9931-c42c097f08b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b99a7-b961-7bca-9c22-bb298b12a75a" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019b99a7-b961-7150-9931-c42c097f08b9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_019b2283-dcf3-74b6-b9c8-42eefe138d32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_019b2283-dcf3-74b6-b9c8-42eefe138d32" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireIntangibleAssets_019b2283-dcf3-741c-82eb-ecd00310972c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireIntangibleAssets"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_PaymentsToAcquireIntangibleAssets_019b2283-dcf3-741c-82eb-ecd00310972c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities_019b2283-dcf3-7a42-97b9-1c127d514874" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities_019b2283-dcf3-7a42-97b9-1c127d514874" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019b2283-dcf3-70d8-8242-e000ade02684" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019b2283-dcf3-70d8-8242-e000ade02684" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019b2283-dcf3-75ab-a636-b988e1a90a39" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019b2283-dcf3-75ab-a636-b988e1a90a39" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_019b2283-dcf3-758b-87b4-6ebf6b1f1925" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfEquityMethodInvestments"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_019b2283-dcf3-758b-87b4-6ebf6b1f1925" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019b2283-dcf3-7227-b939-c307da861f88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019b2283-dcf3-7227-b939-c307da861f88" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries_019b2283-dcf3-7b7b-90cd-3f393745a4e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries_019b2283-dcf3-7b7b-90cd-3f393745a4e3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019b2283-dcf3-7005-988a-45ed455ea51a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019b2283-dcf3-7005-988a-45ed455ea51a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment_019c066e-a3cc-7699-ac79-2674adc15274" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7ca0-8d93-0cfd27dee515" xlink:to="loc_us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment_019c066e-a3cc-7699-ac79-2674adc15274" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019c0563-a085-7ca4-8167-4d76694508d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_ProfitLoss_019c0563-a085-7ca4-8167-4d76694508d7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019c0563-a085-7465-b887-2e3090b0da6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019c0563-a085-7465-b887-2e3090b0da6b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill_019c0563-a086-7689-baf7-00a53fdb3dad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill_019c0563-a086-7689-baf7-00a53fdb3dad" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseImpairmentLoss_019c0563-a086-7669-8fe1-0a507c836ee8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseImpairmentLoss"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_OperatingLeaseImpairmentLoss_019c0563-a086-7669-8fe1-0a507c836ee8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWriteDown_019c0563-a086-75d8-8bc8-adbc7fce251d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryWriteDown"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_InventoryWriteDown_019c0563-a086-75d8-8bc8-adbc7fce251d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_AmortizationOfInventoryStepUp_019c0563-a086-7ea9-ab3b-008db066c1fa" xlink:href="biib-20251231.xsd#biib_AmortizationOfInventoryStepUp"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_biib_AmortizationOfInventoryStepUp_019c0563-a086-7ea9-ab3b-008db066c1fa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentAssetAcquiredOtherThanThroughBusinessCombinationWrittenOff_019c0563-a086-7ae8-9458-3d7477e1bc0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentAssetAcquiredOtherThanThroughBusinessCombinationWrittenOff"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_ResearchAndDevelopmentAssetAcquiredOtherThanThroughBusinessCombinationWrittenOff_019c0563-a086-7ae8-9458-3d7477e1bc0c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019c0563-a086-73e7-9713-ed9961ff7f60" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensation"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_ShareBasedCompensation_019c0563-a086-73e7-9713-ed9961ff7f60" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019c0563-a086-7ee2-a62b-c676e1b15548" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019c0563-a086-7ee2-a62b-c676e1b15548" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019c0563-a086-71a8-9832-d23f29650f70" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019c0563-a086-71a8-9832-d23f29650f70" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInEquitySecuritiesFvNi_019c0563-a086-7b90-9156-de07f376e872" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInEquitySecuritiesFvNi"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_IncreaseDecreaseInEquitySecuritiesFvNi_019c0563-a086-7b90-9156-de07f376e872" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfIntangibleAssets_019c0563-a086-7ba0-a9ce-e1483e08fc6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDispositionOfIntangibleAssets"/>
    <link:calculationArc order="12" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_GainLossOnDispositionOfIntangibleAssets_019c0563-a086-7ba0-a9ce-e1483e08fc6b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_019c0563-a086-7912-b784-5e1fa8449cc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoncashIncomeExpense"/>
    <link:calculationArc order="13" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_019c0563-a086-7912-b784-5e1fa8449cc1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019c0563-a086-7f1a-be12-ce65507c2608" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:calculationArc order="14" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019c0563-a086-7f1a-be12-ce65507c2608" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_019c0563-a086-72c3-8cce-f0ce24f6f6e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet"/>
    <link:calculationArc order="15" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_019c0563-a086-72c3-8cce-f0ce24f6f6e1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_019c0563-a086-7902-89f2-ebe2e68e0a90" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:calculationArc order="16" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_019c0563-a086-7902-89f2-ebe2e68e0a90" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_019c0563-a086-774f-8570-f9c94636e7ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:calculationArc order="17" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_019c0563-a086-774f-8570-f9c94636e7ee" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_019c0563-a086-7e60-a7fc-ba8461ce1ad0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable"/>
    <link:calculationArc order="18" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_019c0563-a086-7e60-a7fc-ba8461ce1ad0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019c0563-a086-746d-9aaf-cd3ce515969e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:calculationArc order="19" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c0563-a085-756e-bddc-856b33927991" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019c0563-a086-746d-9aaf-cd3ce515969e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019b2283-dcf3-77e5-999d-5f05fc1a39a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b2283-dcf3-7c6a-96c7-b0217b047ec9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019b2283-dcf3-77e5-999d-5f05fc1a39a4" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b2283-dcf3-7c6a-96c7-b0217b047ec9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7a3b-8d95-21bb8d032087" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019b2283-dcf3-77e5-999d-5f05fc1a39a4" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b2283-dcf3-7a3b-8d95-21bb8d032087" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019b2283-dcf3-7802-88e6-3c0e4bec3ed9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019b2283-dcf3-77e5-999d-5f05fc1a39a4" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019b2283-dcf3-7802-88e6-3c0e4bec3ed9" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/AcquisitionsPurchasePriceConsiderationDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#AcquisitionsPurchasePriceConsiderationDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/AcquisitionsPurchasePriceConsiderationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2283-dcf4-7b3e-95c0-8ab3351e8728" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_019b2283-dcf4-7970-bf73-039334ad6989" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2283-dcf4-7b3e-95c0-8ab3351e8728" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_019b2283-dcf4-7970-bf73-039334ad6989" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_019b2283-dcf4-7000-9a45-1f74d502ef0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2283-dcf4-7b3e-95c0-8ab3351e8728" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_019b2283-dcf4-7000-9a45-1f74d502ef0c" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/AcquisitionsPurchasePriceConsiderationDetails_1" xlink:type="simple" xlink:href="biib-20251231.xsd#AcquisitionsPurchasePriceConsiderationDetails_1"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/AcquisitionsPurchasePriceConsiderationDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2283-dcf4-76d7-bab2-d3523947f310" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_019b2283-dcf4-74a1-8dff-0e55de808dd2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2283-dcf4-76d7-bab2-d3523947f310" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_019b2283-dcf4-74a1-8dff-0e55de808dd2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_BusinessCombinationConsiderationTransferredEquityCompensationPreAcquisitionServices_019b2283-dcf4-7230-874b-97620b2ccc2f" xlink:href="biib-20251231.xsd#biib_BusinessCombinationConsiderationTransferredEquityCompensationPreAcquisitionServices"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2283-dcf4-76d7-bab2-d3523947f310" xlink:to="loc_biib_BusinessCombinationConsiderationTransferredEquityCompensationPreAcquisitionServices_019b2283-dcf4-7230-874b-97620b2ccc2f" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/AcquisitionsPurchasePriceAllocationDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#AcquisitionsPurchasePriceAllocationDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/AcquisitionsPurchasePriceAllocationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019b2283-dcf4-7437-af67-9ea7fb5d7f07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019b2283-dcf4-743e-8206-1e46ffac507f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019b2283-dcf4-7437-af67-9ea7fb5d7f07" xlink:to="loc_us-gaap_Goodwill_019b2283-dcf4-743e-8206-1e46ffac507f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-71f3-86f1-3dd6b5ab74f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019b2283-dcf4-7437-af67-9ea7fb5d7f07" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-71f3-86f1-3dd6b5ab74f4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_019b2283-dcf4-7e6f-a4cb-17ee251a0c00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_019b2283-dcf4-7e6f-a4cb-17ee251a0c00" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContingentLiability_019b2283-dcf4-7f6e-8fe6-caff902101fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContingentLiability"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContingentLiability_019b2283-dcf4-7f6e-8fe6-caff902101fa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_019b2283-dcf4-7d2d-b34c-eff415c3b950" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_019b2283-dcf4-7d2d-b34c-eff415c3b950" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_019b2283-dcf4-76b5-8926-31c72f59261d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_019b2283-dcf4-76b5-8926-31c72f59261d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_019b2283-dcf4-7455-909d-eb5c0ff3b94e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_019b2283-dcf4-7455-909d-eb5c0ff3b94e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019b2283-dcf4-731f-8eca-b6e06e310d6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019b2283-dcf4-731f-8eca-b6e06e310d6a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_019b2283-dcf4-78cf-95c1-bb6b53b91822" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_019b2283-dcf4-78cf-95c1-bb6b53b91822" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019b2283-dcf4-787c-8314-ef71a26035f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019b2283-dcf4-787c-8314-ef71a26035f9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedLiabilities_019b2283-dcf4-7b86-bff4-a227473aa9b2" xlink:href="biib-20251231.xsd#biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedLiabilities"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedLiabilities_019b2283-dcf4-7b86-bff4-a227473aa9b2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOperatingLeaseAssets_019b2283-dcf4-7775-8e0e-8f5fd59e556a" xlink:href="biib-20251231.xsd#biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOperatingLeaseAssets"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOperatingLeaseAssets_019b2283-dcf4-7775-8e0e-8f5fd59e556a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOperatingLeaseLiabilities_019b2283-dcf4-701b-bc44-e93b83943a40" xlink:href="biib-20251231.xsd#biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOperatingLeaseLiabilities"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_biib_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOperatingLeaseLiabilities_019b2283-dcf4-701b-bc44-e93b83943a40" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_019b2283-dcf4-731b-9556-85363a494fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_019b2283-dcf4-731b-9556-85363a494fe9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_019b2283-dcf4-74e7-ae72-612d9d600d33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities"/>
    <link:calculationArc order="13" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b2283-dcf4-7295-a110-73615717ae3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_019b2283-dcf4-74e7-ae72-612d9d600d33" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/InventoryComponentsofInventoryDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#InventoryComponentsofInventoryDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/InventoryComponentsofInventoryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_biib_InventoryNetCurrentAndNoncurrent_019b2283-dcf4-78a8-9608-09575c0422cb" xlink:href="biib-20251231.xsd#biib_InventoryNetCurrentAndNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryFinishedGoodsNetOfReserves_019b2283-dcf4-7801-b998-927a8335a5af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryFinishedGoodsNetOfReserves"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_biib_InventoryNetCurrentAndNoncurrent_019b2283-dcf4-78a8-9608-09575c0422cb" xlink:to="loc_us-gaap_InventoryFinishedGoodsNetOfReserves_019b2283-dcf4-7801-b998-927a8335a5af" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWorkInProcessNetOfReserves_019b2283-dcf4-77c2-9175-f2e012041f68" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryWorkInProcessNetOfReserves"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_biib_InventoryNetCurrentAndNoncurrent_019b2283-dcf4-78a8-9608-09575c0422cb" xlink:to="loc_us-gaap_InventoryWorkInProcessNetOfReserves_019b2283-dcf4-77c2-9175-f2e012041f68" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryRawMaterialsNetOfReserves_019b2283-dcf4-7855-ad90-b4079b9b81fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryRawMaterialsNetOfReserves"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_biib_InventoryNetCurrentAndNoncurrent_019b2283-dcf4-78a8-9608-09575c0422cb" xlink:to="loc_us-gaap_InventoryRawMaterialsNetOfReserves_019b2283-dcf4-7855-ad90-b4079b9b81fb" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/InventoryComponentsofInventoryDetails_1" xlink:type="simple" xlink:href="biib-20251231.xsd#InventoryComponentsofInventoryDetails_1"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/InventoryComponentsofInventoryDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_biib_InventoryNetCurrentAndNoncurrent_019b2283-dcf4-7a8a-85fc-5e7db1fdad77" xlink:href="biib-20251231.xsd#biib_InventoryNetCurrentAndNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_019b2283-dcf4-749a-9820-97a65ec0882c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNet"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_biib_InventoryNetCurrentAndNoncurrent_019b2283-dcf4-7a8a-85fc-5e7db1fdad77" xlink:to="loc_us-gaap_InventoryNet_019b2283-dcf4-749a-9820-97a65ec0882c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNoncurrent_019b2283-dcf4-76a7-889b-bf267ff1d4b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_biib_InventoryNetCurrentAndNoncurrent_019b2283-dcf4-7a8a-85fc-5e7db1fdad77" xlink:to="loc_us-gaap_InventoryNoncurrent_019b2283-dcf4-76a7-889b-bf267ff1d4b9" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/IntangibleAssetsandGoodwillSummaryofIntangibleAssetsDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#IntangibleAssetsandGoodwillSummaryofIntangibleAssetsDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/IntangibleAssetsandGoodwillSummaryofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b2313-fce5-7c4f-a03e-d9b56a0fc1d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_019b2313-fce5-7efd-8a4d-8b8468096238" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b2313-fce5-7c4f-a03e-d9b56a0fc1d1" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_019b2313-fce5-7efd-8a4d-8b8468096238" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019b2313-fce5-7880-8f93-540a5bbea664" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b2313-fce5-7c4f-a03e-d9b56a0fc1d1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019b2313-fce5-7880-8f93-540a5bbea664" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019b2313-fce5-7a99-8d47-5c9210afaa24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019b2313-fce5-7d0b-ba1c-335c24726e59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019b2313-fce5-7a99-8d47-5c9210afaa24" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019b2313-fce5-7d0b-ba1c-335c24726e59" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019b2313-fce5-765d-ba80-4e39cd3b5fa8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019b2313-fce5-7a99-8d47-5c9210afaa24" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019b2313-fce5-765d-ba80-4e39cd3b5fa8" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/IntangibleAssetsandGoodwillSummaryofIntangibleAssetsDetails_1" xlink:type="simple" xlink:href="biib-20251231.xsd#IntangibleAssetsandGoodwillSummaryofIntangibleAssetsDetails_1"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/IntangibleAssetsandGoodwillSummaryofIntangibleAssetsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b2313-fce5-74ea-ab03-4b6179b90a0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_019b2313-fce5-7e5c-95e2-4b747758aaee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b2313-fce5-74ea-ab03-4b6179b90a0b" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_019b2313-fce5-7e5c-95e2-4b747758aaee" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019b2313-fce5-75d6-9ce9-30b259d419c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b2313-fce5-74ea-ab03-4b6179b90a0b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019b2313-fce5-75d6-9ce9-30b259d419c4" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/FairValueMeasurementsSummaryofAssetsandLiabilitiesRecordedatFairValueDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#FairValueMeasurementsSummaryofAssetsandLiabilitiesRecordedatFairValueDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/FairValueMeasurementsSummaryofAssetsandLiabilitiesRecordedatFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019b9a10-7370-7bc1-a3f4-bfa51e17d6d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019b9a10-7370-7594-8af0-d75ba203eb3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019b9a10-7370-7bc1-a3f4-bfa51e17d6d2" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019b9a10-7370-7594-8af0-d75ba203eb3d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019b9a10-7370-74a8-b514-9854d637114e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019b9a10-7370-7bc1-a3f4-bfa51e17d6d2" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019b9a10-7370-74a8-b514-9854d637114e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_019b9a10-7370-7d9c-8bc3-9a002f136eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019b9a10-7370-7bc1-a3f4-bfa51e17d6d2" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_019b9a10-7370-7d9c-8bc3-9a002f136eaf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsCurrent_019b9a10-7370-7331-aa65-5425aaab210c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019b9a10-7370-7bc1-a3f4-bfa51e17d6d2" xlink:to="loc_us-gaap_DerivativeAssetsCurrent_019b9a10-7370-7331-aa65-5425aaab210c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableFairValueDisclosure_019b9a10-7370-7b65-b2a7-ecc05e19f67c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesReceivableFairValueDisclosure"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019b9a10-7370-7bc1-a3f4-bfa51e17d6d2" xlink:to="loc_us-gaap_NotesReceivableFairValueDisclosure_019b9a10-7370-7b65-b2a7-ecc05e19f67c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_PlanAssetsForDeferredCompensationFairValueDisclosure_019b9a10-7370-7ffa-ad01-710079b06c69" xlink:href="biib-20251231.xsd#biib_PlanAssetsForDeferredCompensationFairValueDisclosure"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019b9a10-7370-7bc1-a3f4-bfa51e17d6d2" xlink:to="loc_biib_PlanAssetsForDeferredCompensationFairValueDisclosure_019b9a10-7370-7ffa-ad01-710079b06c69" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019bebed-501d-7c35-a68e-3ffa55ca0289" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_019b9a10-7370-7bc1-a3f4-bfa51e17d6d2" xlink:to="loc_us-gaap_DerivativeAssets_019bebed-501d-7c35-a68e-3ffa55ca0289" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019b232d-2fef-7bf4-b07a-a288b003c23c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_019b232d-2fef-761d-841b-b89027c980bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosure_019b232d-2fef-7bf4-b07a-a288b003c23c" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_019b232d-2fef-761d-841b-b89027c980bf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019b232d-2fef-75d5-b44d-7af8c9418a5f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosure_019b232d-2fef-7bf4-b07a-a288b003c23c" xlink:to="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019b232d-2fef-75d5-b44d-7af8c9418a5f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_019b232d-2fef-72ff-83e4-f052a03b37e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosure_019b232d-2fef-7bf4-b07a-a288b003c23c" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_019b232d-2fef-72ff-83e4-f052a03b37e8" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/FinancialInstrumentsSummaryofContractualMaturitiesDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#FinancialInstrumentsSummaryofContractualMaturitiesDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/FinancialInstrumentsSummaryofContractualMaturitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019bebfa-b397-7395-aabe-6c3716763d5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_019bebfa-b397-7c2c-bac3-8920a85cf4ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019bebfa-b397-7395-aabe-6c3716763d5c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_019bebfa-b397-7c2c-bac3-8920a85cf4ea" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_019bebfa-b397-7125-87be-1e22e154df1a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019bebfa-b397-7395-aabe-6c3716763d5c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_019bebfa-b397-7125-87be-1e22e154df1a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_DebtSecuritiesAvailableForSaleFairValueMaturityAllocatedAndSingleMaturityDateAfterYear5_019bebfa-b397-715e-acad-933d9248ea6f" xlink:href="biib-20251231.xsd#biib_DebtSecuritiesAvailableForSaleFairValueMaturityAllocatedAndSingleMaturityDateAfterYear5"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019bebfa-b397-7395-aabe-6c3716763d5c" xlink:to="loc_biib_DebtSecuritiesAvailableForSaleFairValueMaturityAllocatedAndSingleMaturityDateAfterYear5_019bebfa-b397-715e-acad-933d9248ea6f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019bebfc-0617-7775-8ca8-10197c322d28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_019bebfc-0617-7e23-b668-dfd0e85ebbaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019bebfc-0617-7775-8ca8-10197c322d28" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_019bebfc-0617-7e23-b668-dfd0e85ebbaf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_019bebfc-0617-78de-90dc-1421841c94d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019bebfc-0617-7775-8ca8-10197c322d28" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_019bebfc-0617-78de-90dc-1421841c94d3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_DebtSecuritiesAvailableForSaleAmortizedCostMaturityAllocatedAndSingleMaturityDateAfterYear5_019bebfc-0617-70ad-aa01-3c2518ad1b79" xlink:href="biib-20251231.xsd#biib_DebtSecuritiesAvailableForSaleAmortizedCostMaturityAllocatedAndSingleMaturityDateAfterYear5"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019bebfc-0617-7775-8ca8-10197c322d28" xlink:to="loc_biib_DebtSecuritiesAvailableForSaleAmortizedCostMaturityAllocatedAndSingleMaturityDateAfterYear5_019bebfc-0617-70ad-aa01-3c2518ad1b79" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/DerivativeInstrumentsSummaryofUnrealizedGainLossonDerivativeInstrumentsIncludedinAOCIDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#DerivativeInstrumentsSummaryofUnrealizedGainLossonDerivativeInstrumentsIncludedinAOCIDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/DerivativeInstrumentsSummaryofUnrealizedGainLossonDerivativeInstrumentsIncludedinAOCIDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_019b2283-ddb0-7936-b1f7-bdd7922c172f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_UnrealizedLossOnDerivatives_019b2283-ddb0-7afb-bc2d-a54cb9716fac" xlink:href="biib-20251231.xsd#biib_UnrealizedLossOnDerivatives"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_UnrealizedGainLossOnDerivatives_019b2283-ddb0-7936-b1f7-bdd7922c172f" xlink:to="loc_biib_UnrealizedLossOnDerivatives_019b2283-ddb0-7afb-bc2d-a54cb9716fac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_UnrealizedGainOnDerivatives_019b2283-ddb0-7810-a4b4-5633986264cb" xlink:href="biib-20251231.xsd#biib_UnrealizedGainOnDerivatives"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_UnrealizedGainLossOnDerivatives_019b2283-ddb0-7936-b1f7-bdd7922c172f" xlink:to="loc_biib_UnrealizedGainOnDerivatives_019b2283-ddb0-7810-a4b4-5633986264cb" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/PropertyPlantandEquipmentComponentsofpropertyplantandequipmentnetDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#PropertyPlantandEquipmentComponentsofpropertyplantandequipmentnetDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/PropertyPlantandEquipmentComponentsofpropertyplantandequipmentnetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7a41-add9-fc9017a55699" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Land_019b2283-ddb0-7e44-b8f4-5c55f43ce54a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Land"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7a41-add9-fc9017a55699" xlink:to="loc_us-gaap_Land_019b2283-ddb0-7e44-b8f4-5c55f43ce54a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingsAndImprovementsGross_019b2283-ddb0-7c05-99f6-0ca76ce9624b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BuildingsAndImprovementsGross"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7a41-add9-fc9017a55699" xlink:to="loc_us-gaap_BuildingsAndImprovementsGross_019b2283-ddb0-7c05-99f6-0ca76ce9624b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsGross_019b2283-ddb0-74e2-96a6-d6cb4ff0d131" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeaseholdImprovementsGross"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7a41-add9-fc9017a55699" xlink:to="loc_us-gaap_LeaseholdImprovementsGross_019b2283-ddb0-74e2-96a6-d6cb4ff0d131" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentGross_019b2283-ddb0-78aa-9ee0-c2de8c7e91ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MachineryAndEquipmentGross"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7a41-add9-fc9017a55699" xlink:to="loc_us-gaap_MachineryAndEquipmentGross_019b2283-ddb0-78aa-9ee0-c2de8c7e91ff" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_ComputerSoftwareAndHardware_019b2283-ddb0-7feb-bdd2-8dce43ab0c81" xlink:href="biib-20251231.xsd#biib_ComputerSoftwareAndHardware"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7a41-add9-fc9017a55699" xlink:to="loc_biib_ComputerSoftwareAndHardware_019b2283-ddb0-7feb-bdd2-8dce43ab0c81" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesGross_019b2283-ddb0-7154-9f0e-b01c1fac80e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FurnitureAndFixturesGross"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7a41-add9-fc9017a55699" xlink:to="loc_us-gaap_FurnitureAndFixturesGross_019b2283-ddb0-7154-9f0e-b01c1fac80e0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressGross_019b2283-ddb0-7680-8716-22f55124b672" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConstructionInProgressGross"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7a41-add9-fc9017a55699" xlink:to="loc_us-gaap_ConstructionInProgressGross_019b2283-ddb0-7680-8716-22f55124b672" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019b2283-ddb0-7eeb-9bdf-123751032da8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7e6b-81a9-116f8477965d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNet_019b2283-ddb0-7eeb-9bdf-123751032da8" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_019b2283-ddb0-7e6b-81a9-116f8477965d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019b2283-ddb0-75d1-afcc-ed840afc9518" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNet_019b2283-ddb0-7eeb-9bdf-123751032da8" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019b2283-ddb0-75d1-afcc-ed840afc9518" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/LeasesOperatingLeaseCostsDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#LeasesOperatingLeaseCostsDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/LeasesOperatingLeaseCostsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCost_019b2283-ddb0-71f7-80d3-31f9eddb3742" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeaseCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubleaseIncome_019b2283-ddb0-71db-9441-d40c5b37948d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubleaseIncome"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019b2283-ddb0-71f7-80d3-31f9eddb3742" xlink:to="loc_us-gaap_SubleaseIncome_019b2283-ddb0-71db-9441-d40c5b37948d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_019b2283-ddb0-7311-b4a7-bdd5aa933cde" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseCost"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019b2283-ddb0-71f7-80d3-31f9eddb3742" xlink:to="loc_us-gaap_OperatingLeaseCost_019b2283-ddb0-7311-b4a7-bdd5aa933cde" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableLeaseCost_019b2283-ddb0-752d-b133-4c4e5f9fac61" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableLeaseCost"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019b2283-ddb0-71f7-80d3-31f9eddb3742" xlink:to="loc_us-gaap_VariableLeaseCost_019b2283-ddb0-752d-b133-4c4e5f9fac61" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/LeasesOperatingLeaseLiabilityMaturityDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#LeasesOperatingLeaseLiabilityMaturityDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/LeasesOperatingLeaseLiabilityMaturityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7110-859d-c7cabe468e82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019b2283-ddb0-7ecb-b036-e3b023097313" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7110-859d-c7cabe468e82" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019b2283-ddb0-7ecb-b036-e3b023097313" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_019b2283-ddb0-7951-bbb8-5ee57a980e2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7110-859d-c7cabe468e82" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_019b2283-ddb0-7951-bbb8-5ee57a980e2b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019b2283-ddb0-7825-85b4-42e74abc4504" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7110-859d-c7cabe468e82" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019b2283-ddb0-7825-85b4-42e74abc4504" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_019b2283-ddb0-7da8-a3d5-3b475edba19d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7110-859d-c7cabe468e82" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_019b2283-ddb0-7da8-a3d5-3b475edba19d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019b2283-ddb0-7707-b50a-4dd1772eeb64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7110-859d-c7cabe468e82" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019b2283-ddb0-7707-b50a-4dd1772eeb64" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019b2283-ddb0-7a6f-9f02-add9634aaae5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7110-859d-c7cabe468e82" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019b2283-ddb0-7a6f-9f02-add9634aaae5" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/LeasesOperatingLeaseLiabilityMaturityDetails_1" xlink:type="simple" xlink:href="biib-20251231.xsd#LeasesOperatingLeaseLiabilityMaturityDetails_1"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/LeasesOperatingLeaseLiabilityMaturityDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7c7e-b2fe-35e76df700d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019b2283-ddb0-700c-8a2b-81422362cc92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7c7e-b2fe-35e76df700d3" xlink:to="loc_us-gaap_OperatingLeaseLiability_019b2283-ddb0-700c-8a2b-81422362cc92" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019b2283-ddb0-70d0-86fd-dfc25d50fe3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b2283-ddb0-7c7e-b2fe-35e76df700d3" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019b2283-ddb0-70d0-86fd-dfc25d50fe3e" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/IndebtednessTotalDebtMaturitiesDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#IndebtednessTotalDebtMaturitiesDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/IndebtednessTotalDebtMaturitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019b2283-ddb0-70c9-bec6-3ff681bfd36c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-7f71-b70a-f49cc69d07a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019b2283-ddb0-70c9-bec6-3ff681bfd36c" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-7f71-b70a-f49cc69d07a6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019b2283-ddb0-7768-a83a-940fc9730d59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019b2283-ddb0-70c9-bec6-3ff681bfd36c" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019b2283-ddb0-7768-a83a-940fc9730d59" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-73b0-9a27-d2f42a3ab80a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019b2283-ddb0-7d31-b611-4fb2d02a05b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-73b0-9a27-d2f42a3ab80a" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019b2283-ddb0-7d31-b611-4fb2d02a05b6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_019b2283-ddb0-7a7c-81f5-e795f7bfea32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-73b0-9a27-d2f42a3ab80a" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_019b2283-ddb0-7a7c-81f5-e795f7bfea32" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_019b2283-ddb0-7417-be8a-1f57d571265b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-73b0-9a27-d2f42a3ab80a" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_019b2283-ddb0-7417-be8a-1f57d571265b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019b2283-ddb0-78b8-b5cb-0ab9e1e36cd7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-73b0-9a27-d2f42a3ab80a" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019b2283-ddb0-78b8-b5cb-0ab9e1e36cd7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019b2283-ddb0-7e94-96b8-45dca6fc0d32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-73b0-9a27-d2f42a3ab80a" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019b2283-ddb0-7e94-96b8-45dca6fc0d32" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019b2283-ddb0-7960-a4d2-e9bd0ca39ebf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b2283-ddb0-73b0-9a27-d2f42a3ab80a" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019b2283-ddb0-7960-a4d2-e9bd0ca39ebf" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/EquityAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#EquityAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/EquityAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2359-5428-733e-afdc-4e7fd4212fba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019b2359-5428-7a90-8975-350bdf6eeecf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2359-5428-733e-afdc-4e7fd4212fba" xlink:to="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019b2359-5428-7a90-8975-350bdf6eeecf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019b2359-5428-7d37-bd72-429d919071cc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019b2359-5428-733e-afdc-4e7fd4212fba" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019b2359-5428-7d37-bd72-429d919071cc" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/EquityReclassificationoutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#EquityReclassificationoutofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/EquityReclassificationoutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019b2283-ddb0-7380-8763-472bd0e74f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019b2283-ddb0-761d-829f-78aa8a349195" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-ddb0-7380-8763-472bd0e74f3c" xlink:to="loc_us-gaap_Revenues_019b2283-ddb0-761d-829f-78aa8a349195" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019b2283-ddb0-7939-aabf-170226ea4e7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpenses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-ddb0-7380-8763-472bd0e74f3c" xlink:to="loc_us-gaap_OperatingExpenses_019b2283-ddb0-7939-aabf-170226ea4e7d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncomeExpenseNet_019b2283-ddb0-7fd8-87ce-cbc0abe140bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherOperatingIncomeExpenseNet"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-ddb0-7380-8763-472bd0e74f3c" xlink:to="loc_us-gaap_OtherOperatingIncomeExpenseNet_019b2283-ddb0-7fd8-87ce-cbc0abe140bb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019b2283-ddb0-7e17-9354-7e9cbfe2cf09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-ddb0-7380-8763-472bd0e74f3c" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019b2283-ddb0-7e17-9354-7e9cbfe2cf09" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/EarningsperShareBasicandDilutedEarningsPerShareDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#EarningsperShareBasicandDilutedEarningsPerShareDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/EarningsperShareBasicandDilutedEarningsPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019b2283-ddb0-7124-ad37-dfb593cbff49" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019b2283-ddb0-7f39-b84e-52ad915fdc7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019b2283-ddb0-7124-ad37-dfb593cbff49" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019b2283-ddb0-7f39-b84e-52ad915fdc7d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019b2283-ddb0-740b-b40a-7665478ef40b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019b2283-ddb0-7e96-9312-888536e28889" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019b2283-ddb0-740b-b40a-7665478ef40b" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019b2283-ddb0-7e96-9312-888536e28889" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019b2283-ddb0-7e5c-bcae-776b73732f20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019b2283-ddb0-740b-b40a-7665478ef40b" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019b2283-ddb0-7e5c-bcae-776b73732f20" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/ShareBasedPaymentsSharebasedCompensationExpenseIncludedinConsolidationStatementsofIncomeDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#ShareBasedPaymentsSharebasedCompensationExpenseIncludedinConsolidationStatementsofIncomeDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/ShareBasedPaymentsSharebasedCompensationExpenseIncludedinConsolidationStatementsofIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax_019b2283-ddb0-73d5-beff-7e8b557a0abd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_019b2283-ddb0-701e-ab1a-fde7ecce242b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax_019b2283-ddb0-73d5-beff-7e8b557a0abd" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_019b2283-ddb0-701e-ab1a-fde7ecce242b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_ShareBasedCompensationExpenseIncludedInCostsAndExpenses_019b2283-ddb0-7bd0-b23c-82a8b2bef689" xlink:href="biib-20251231.xsd#biib_ShareBasedCompensationExpenseIncludedInCostsAndExpenses"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax_019b2283-ddb0-73d5-beff-7e8b557a0abd" xlink:to="loc_biib_ShareBasedCompensationExpenseIncludedInCostsAndExpenses_019b2283-ddb0-7bd0-b23c-82a8b2bef689" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/IncomeTaxesIncomeBeforeIncomeTaxProvisionandtheIncomeTaxExpenseDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#IncomeTaxesIncomeBeforeIncomeTaxProvisionandtheIncomeTaxExpenseDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/IncomeTaxesIncomeBeforeIncomeTaxProvisionandtheIncomeTaxExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b2283-ddb0-7347-9ebf-bc75b18c94ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFederalIncomeTaxExpenseBenefit_019b2283-ddb0-761d-9bf5-1e1e5d65cdab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFederalIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b2283-ddb0-7347-9ebf-bc75b18c94ac" xlink:to="loc_us-gaap_DeferredFederalIncomeTaxExpenseBenefit_019b2283-ddb0-761d-9bf5-1e1e5d65cdab" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit_019b2283-ddb0-7201-a117-f0560795f537" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b2283-ddb0-7347-9ebf-bc75b18c94ac" xlink:to="loc_us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit_019b2283-ddb0-7201-a117-f0560795f537" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredForeignIncomeTaxExpenseBenefit_019b2283-ddb0-7065-b4d5-1b289d983ac2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredForeignIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b2283-ddb0-7347-9ebf-bc75b18c94ac" xlink:to="loc_us-gaap_DeferredForeignIncomeTaxExpenseBenefit_019b2283-ddb0-7065-b4d5-1b289d983ac2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019b2283-ddb0-7523-b762-e6db2cb29db4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b2283-ddb0-7b04-a3bc-a18a50e57ce2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019b2283-ddb0-7523-b762-e6db2cb29db4" xlink:to="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b2283-ddb0-7b04-a3bc-a18a50e57ce2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b2283-ddb0-7ad2-be15-abcb904e2cdd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019b2283-ddb0-7523-b762-e6db2cb29db4" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b2283-ddb0-7ad2-be15-abcb904e2cdd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2283-ddb0-7061-8d72-a92bcde76a4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic_019b2283-ddb0-7a6d-a470-e2f7930bc900" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2283-ddb0-7061-8d72-a92bcde76a4c" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic_019b2283-ddb0-7a6d-a470-e2f7930bc900" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign_019b2283-ddb0-7e02-a167-ffe33e52b086" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2283-ddb0-7061-8d72-a92bcde76a4c" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign_019b2283-ddb0-7e02-a167-ffe33e52b086" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b2283-ddb0-7c6b-b1c0-aeb801e015d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentFederalTaxExpenseBenefit_019b2283-ddb0-7b4f-a24c-10e86e867ff2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentFederalTaxExpenseBenefit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b2283-ddb0-7c6b-b1c0-aeb801e015d2" xlink:to="loc_us-gaap_CurrentFederalTaxExpenseBenefit_019b2283-ddb0-7b4f-a24c-10e86e867ff2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentStateAndLocalTaxExpenseBenefit_019b2283-ddb0-7549-88aa-a43e1eb28bcc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentStateAndLocalTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b2283-ddb0-7c6b-b1c0-aeb801e015d2" xlink:to="loc_us-gaap_CurrentStateAndLocalTaxExpenseBenefit_019b2283-ddb0-7549-88aa-a43e1eb28bcc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentForeignTaxExpenseBenefit_019b2283-ddb0-7fb5-b225-d2cd1fc7fefc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentForeignTaxExpenseBenefit"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b2283-ddb0-7c6b-b1c0-aeb801e015d2" xlink:to="loc_us-gaap_CurrentForeignTaxExpenseBenefit_019b2283-ddb0-7fb5-b225-d2cd1fc7fefc" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/IncomeTaxesComponentsofDeferredTaxAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#IncomeTaxesComponentsofDeferredTaxAssetsandLiabilitiesDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/IncomeTaxesComponentsofDeferredTaxAssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxLiabilities_019b2283-ddb0-7e9c-aa03-b8c42a7e96f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_DeferredTaxLiabilitiesDepreciationAmortizationOther_019b2283-ddb0-7a05-a394-9efeff496f98" xlink:href="biib-20251231.xsd#biib_DeferredTaxLiabilitiesDepreciationAmortizationOther"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_019b2283-ddb0-7e9c-aa03-b8c42a7e96f3" xlink:to="loc_biib_DeferredTaxLiabilitiesDepreciationAmortizationOther_019b2283-ddb0-7a05-a394-9efeff496f98" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets_019b2283-ddb0-7ba8-811e-5a877cf6cdec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_019b2283-ddb0-7e9c-aa03-b8c42a7e96f3" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets_019b2283-ddb0-7ba8-811e-5a877cf6cdec" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_DeferredTaxLiabilitiesGILTITaxCalculation_019b2283-ddb0-7919-9e36-49b16a33a6f1" xlink:href="biib-20251231.xsd#biib_DeferredTaxLiabilitiesGILTITaxCalculation"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_019b2283-ddb0-7e9c-aa03-b8c42a7e96f3" xlink:to="loc_biib_DeferredTaxLiabilitiesGILTITaxCalculation_019b2283-ddb0-7919-9e36-49b16a33a6f1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwards_019b2283-ddb0-7a91-a5e6-d389c671fa78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwards"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwards_019b2283-ddb0-7a91-a5e6-d389c671fa78" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets_019b2283-ddb0-7a9d-9b4f-2c99d0fc8bd6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:to="loc_us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets_019b2283-ddb0-7a9d-9b4f-2c99d0fc8bd6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsInProcessResearchAndDevelopment_019b2283-ddb0-792d-aaa4-f9fe58212725" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsInProcessResearchAndDevelopment"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:to="loc_us-gaap_DeferredTaxAssetsInProcessResearchAndDevelopment_019b2283-ddb0-792d-aaa4-f9fe58212725" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_019b2283-ddb0-79a3-9e72-a23cf168a2d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_019b2283-ddb0-79a3-9e72-a23cf168a2d1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwards_019b2283-ddb0-7b44-9701-b1f6654a3e8d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwards"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:to="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwards_019b2283-ddb0-7b44-9701-b1f6654a3e8d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsOther_019b2283-ddb0-7937-85fa-9d3172f623be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsOther"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:to="loc_us-gaap_DeferredTaxAssetsOther_019b2283-ddb0-7937-85fa-9d3172f623be" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance_019b2283-ddb0-725b-91db-639d8b76f21f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:to="loc_us-gaap_DeferredTaxAssetsValuationAllowance_019b2283-ddb0-725b-91db-639d8b76f21f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsInventory_019b2283-ddb0-75d9-b491-3615b47c2e90" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsInventory"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b2283-ddb0-7800-a71a-527185206f6f" xlink:to="loc_us-gaap_DeferredTaxAssetsInventory_019b2283-ddb0-75d9-b491-3615b47c2e90" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/IncomeTaxesTaxRateDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#IncomeTaxesTaxRateDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/IncomeTaxesTaxRateDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_019c061e-b855-75f5-ae39-a41da77525ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_019c061e-b855-75f5-ae39-a41da77525ad" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_019c061e-b855-73b3-87c9-5dacb060e42c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_019c061e-b855-73b3-87c9-5dacb060e42c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationWithholdingTaxAmount_019c061e-b855-7146-a138-5c4cc605968d" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationWithholdingTaxAmount"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationWithholdingTaxAmount_019c061e-b855-7146-a138-5c4cc605968d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationOtherAdjustments_019c061e-b855-7488-b8f5-e34ebe8232e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationOtherAdjustments"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationOtherAdjustments_019c061e-b855-7488-b8f5-e34ebe8232e6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential_019c061e-b855-7beb-a3c7-154ae038d79d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential_019c061e-b855-7beb-a3c7-154ae038d79d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationCantonalTaxImpactAmount_019c061e-b855-7f92-895d-3dbc4be187ca" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationCantonalTaxImpactAmount"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationCantonalTaxImpactAmount_019c061e-b855-7f92-895d-3dbc4be187ca" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationPillarTwoTaxesAmount_019c061e-b855-7bbc-9764-45fb5f2d4dcb" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationPillarTwoTaxesAmount"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationPillarTwoTaxesAmount_019c061e-b855-7bbc-9764-45fb5f2d4dcb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_019c061e-b855-7f6d-baaa-59d5eee4d6a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_019c061e-b855-7f6d-baaa-59d5eee4d6a3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationEquityInEarningsLossesOfUnconsolidatedSubsidiary_019c061e-b855-7d1b-856c-269e2fe84876" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationEquityInEarningsLossesOfUnconsolidatedSubsidiary"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationEquityInEarningsLossesOfUnconsolidatedSubsidiary_019c061e-b855-7d1b-856c-269e2fe84876" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationLitigationAmount_019c061e-b855-7758-b22a-c6634d0b1299" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationLitigationAmount"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationLitigationAmount_019c061e-b855-7758-b22a-c6634d0b1299" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate_019c061e-b855-723d-91dc-e6a81bfa547a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate"/>
    <link:calculationArc order="11" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate_019c061e-b855-723d-91dc-e6a81bfa547a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationGiltiAmount_019c061e-b855-7bd1-ba74-4e79181191fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationGiltiAmount"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationGiltiAmount_019c061e-b855-7bd1-ba74-4e79181191fc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationCrossBorderOtherAmount_019c061e-b855-791b-bfd6-6b9396c8804f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationCrossBorderOtherAmount"/>
    <link:calculationArc order="13" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationCrossBorderOtherAmount_019c061e-b855-791b-bfd6-6b9396c8804f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationTaxCreditsResearch_019c061e-b855-76d8-8d55-4b0c49ba267f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationTaxCreditsResearch"/>
    <link:calculationArc order="14" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationTaxCreditsResearch_019c061e-b855-76d8-8d55-4b0c49ba267f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationTaxCreditsOther_019c061e-b855-709e-9c3f-bcec29ec0fb3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationTaxCreditsOther"/>
    <link:calculationArc order="15" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationTaxCreditsOther_019c061e-b855-709e-9c3f-bcec29ec0fb3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost_019c061e-b855-721f-931d-40ce4d0fc529" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost"/>
    <link:calculationArc order="16" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost_019c061e-b855-721f-931d-40ce4d0fc529" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther_019c061e-b855-745f-a2e0-ef944aefc27c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther"/>
    <link:calculationArc order="17" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther_019c061e-b855-745f-a2e0-ef944aefc27c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationTaxContingencies_019c061e-b855-75f8-853e-5cb4021a43d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationTaxContingencies"/>
    <link:calculationArc order="18" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c061e-b855-7bba-9659-42d045c11475" xlink:to="loc_us-gaap_IncomeTaxReconciliationTaxContingencies_019c061e-b855-75f8-853e-5cb4021a43d2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_019c1179-1bf8-72aa-a873-628c17a6063f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_019c1179-1bf8-72aa-a873-628c17a6063f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_019c1179-1bf8-728c-a78c-281604609e78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_019c1179-1bf8-728c-a78c-281604609e78" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationWithholdingTaxPercent_019c1179-1bf8-71b6-915c-e027b33dd14c" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationWithholdingTaxPercent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationWithholdingTaxPercent_019c1179-1bf8-71b6-915c-e027b33dd14c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_019c1179-1bf8-7236-bff9-ee1f939797e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_019c1179-1bf8-7236-bff9-ee1f939797e8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_019c1179-1bf8-79e4-8e6a-4ae814447d03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_019c1179-1bf8-79e4-8e6a-4ae814447d03" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationCantonalTaxImpactPercent_019c1179-1bf8-79a9-9d88-e724c10116fc" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationCantonalTaxImpactPercent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationCantonalTaxImpactPercent_019c1179-1bf8-79a9-9d88-e724c10116fc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationPillarTwoTaxesPercent_019c1179-1bf8-73dd-b2f0-bf68726fa6ad" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationPillarTwoTaxesPercent"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationPillarTwoTaxesPercent_019c1179-1bf8-73dd-b2f0-bf68726fa6ad" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance_019c1179-1bf8-706c-8916-920af4ca2e05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance_019c1179-1bf8-706c-8916-920af4ca2e05" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationEquityInEarningsLossesOfUnconsolidatedSubsidiary_019c1179-1bf8-70d6-bd51-3f6d33b5a9ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationEquityInEarningsLossesOfUnconsolidatedSubsidiary"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationEquityInEarningsLossesOfUnconsolidatedSubsidiary_019c1179-1bf8-70d6-bd51-3f6d33b5a9ac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationLitigationPercent_019c1179-1bf8-71d2-8b2e-0cca70b21f17" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationLitigationPercent"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationLitigationPercent_019c1179-1bf8-71d2-8b2e-0cca70b21f17" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate_019c1179-1bf8-7dc1-85ba-cc7bfdde11f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate"/>
    <link:calculationArc order="11" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate_019c1179-1bf8-7dc1-85ba-cc7bfdde11f4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationGiltiPercent_019c1179-1bf8-7fe6-b7b0-67a2f415509a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationGiltiPercent"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationGiltiPercent_019c1179-1bf8-7fe6-b7b0-67a2f415509a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationCrossBorderOtherPercent_019c1179-1bf8-7263-a027-0a56d604bc7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationCrossBorderOtherPercent"/>
    <link:calculationArc order="13" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationCrossBorderOtherPercent_019c1179-1bf8-7263-a027-0a56d604bc7a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsResearch_019c1179-1bf8-7ac9-a892-5921641275a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsResearch"/>
    <link:calculationArc order="14" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsResearch_019c1179-1bf8-7ac9-a892-5921641275a3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsOther_019c1179-1bf8-771a-9ce8-5c4c1d9fca93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsOther"/>
    <link:calculationArc order="15" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsOther_019c1179-1bf8-771a-9ce8-5c4c1d9fca93" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost_019c1179-1bf8-7b79-a4fe-33cba2956305" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost"/>
    <link:calculationArc order="16" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost_019c1179-1bf8-7b79-a4fe-33cba2956305" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther_019c1179-1bf8-74f0-8e08-f733fab46c41" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther"/>
    <link:calculationArc order="17" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther_019c1179-1bf8-74f0-8e08-f733fab46c41" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxContingencies_019c1179-1bf8-7dad-aa6a-b1e1c978596d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxContingencies"/>
    <link:calculationArc order="18" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxContingencies_019c1179-1bf8-7dad-aa6a-b1e1c978596d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciationAndAmortization_019c1179-1bf8-7045-95b1-9b3db58e618d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciationAndAmortization"/>
    <link:calculationArc order="19" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciationAndAmortization_019c1179-1bf8-7045-95b1-9b3db58e618d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_EffectiveIncomeTaxRateReconciliationIntellectualPropertyRightsReorganization_019c1179-1bf8-7cff-82f0-8bac45c560c9" xlink:href="biib-20251231.xsd#biib_EffectiveIncomeTaxRateReconciliationIntellectualPropertyRightsReorganization"/>
    <link:calculationArc order="20" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c1179-1bf8-73f1-a52e-ee34b6bc52cf" xlink:to="loc_biib_EffectiveIncomeTaxRateReconciliationIntellectualPropertyRightsReorganization_019c1179-1bf8-7cff-82f0-8bac45c560c9" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/IncomeTaxesIncomeTaxesPaidDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#IncomeTaxesIncomeTaxesPaidDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/IncomeTaxesIncomeTaxesPaidDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_019c0625-b2c8-7e5f-abfe-7fea25409c2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxesPaidNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidFederalAfterRefundReceived_019c0625-b2c8-71f6-a812-dfc0bef37d2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidFederalAfterRefundReceived"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxesPaidNet_019c0625-b2c8-7e5f-abfe-7fea25409c2c" xlink:to="loc_us-gaap_IncomeTaxPaidFederalAfterRefundReceived_019c0625-b2c8-71f6-a812-dfc0bef37d2b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived_019c0625-b2c8-747e-a8b5-02416f24427d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxesPaidNet_019c0625-b2c8-7e5f-abfe-7fea25409c2c" xlink:to="loc_us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived_019c0625-b2c8-747e-a8b5-02416f24427d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidForeignAfterRefundReceived_019c0625-b2c8-7553-bfc9-44ad4b042912" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidForeignAfterRefundReceived"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxesPaidNet_019c0625-b2c8-7e5f-abfe-7fea25409c2c" xlink:to="loc_us-gaap_IncomeTaxPaidForeignAfterRefundReceived_019c0625-b2c8-7553-bfc9-44ad4b042912" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/OtherConsolidatedFinancialStatementDetailAccruedExpenseandOtherDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#OtherConsolidatedFinancialStatementDetailAccruedExpenseandOtherDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/OtherConsolidatedFinancialStatementDetailAccruedExpenseandOtherDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-de7d-7f29-847e-4a745e402e95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_019b2283-de7d-7272-b823-5e2d652d9df7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-de7d-7f29-847e-4a745e402e95" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesBalance_019b2283-de7d-7272-b823-5e2d652d9df7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_019b2283-de7d-7d8f-8537-b8824829e2a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-de7d-7f29-847e-4a745e402e95" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_019b2283-de7d-7d8f-8537-b8824829e2a6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_biib_CollaborationExpensesAccrual_019b2283-de7d-7ace-aadd-e5ba9134b1a2" xlink:href="biib-20251231.xsd#biib_CollaborationExpensesAccrual"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-de7d-7f29-847e-4a745e402e95" xlink:to="loc_biib_CollaborationExpensesAccrual_019b2283-de7d-7ace-aadd-e5ba9134b1a2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019b2283-de7d-79b1-934a-439a22dac13e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-de7d-7f29-847e-4a745e402e95" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019b2283-de7d-79b1-934a-439a22dac13e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019b2283-de7d-7a14-af56-da2cae74a55e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAccruedLiabilitiesCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-de7d-7f29-847e-4a745e402e95" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019b2283-de7d-7a14-af56-da2cae74a55e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedRoyaltiesCurrent_019b2283-de7d-7fbd-b3f4-7bf3b6975f8c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedRoyaltiesCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b2283-de7d-7f29-847e-4a745e402e95" xlink:to="loc_us-gaap_AccruedRoyaltiesCurrent_019b2283-de7d-7fbd-b3f4-7bf3b6975f8c" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/OtherConsolidatedFinancialStatementDetailGainLossonInvestmentsDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#OtherConsolidatedFinancialStatementDetailGainLossonInvestmentsDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/OtherConsolidatedFinancialStatementDetailGainLossonInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiGainLoss_019b2283-de7d-7cdf-aa96-a8d9114bff7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesFvNiGainLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss_019b2283-de7d-7f91-8e50-cb6d18da50db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EquitySecuritiesFvNiGainLoss_019b2283-de7d-7cdf-aa96-a8d9114bff7a" xlink:to="loc_us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss_019b2283-de7d-7f91-8e50-cb6d18da50db" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_019b2283-de7d-7695-bc13-f3d38678f462" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesFvNiRealizedGainLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EquitySecuritiesFvNiGainLoss_019b2283-de7d-7cdf-aa96-a8d9114bff7a" xlink:to="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_019b2283-de7d-7695-bc13-f3d38678f462" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.biogenidec.com/role/SegmentInformationAdditionalSegmentInformationDetails" xlink:type="simple" xlink:href="biib-20251231.xsd#SegmentInformationAdditionalSegmentInformationDetails"/>
  <link:calculationLink xlink:role="http://www.biogenidec.com/role/SegmentInformationAdditionalSegmentInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019b2283-de7d-79aa-8444-de3eda813570" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019b2283-de7d-7788-b587-ae90d73e3f7c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-de7d-79aa-8444-de3eda813570" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019b2283-de7d-7788-b587-ae90d73e3f7c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_019b2283-de7d-7796-ad7b-6562f60162ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-de7d-79aa-8444-de3eda813570" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_019b2283-de7d-7796-ad7b-6562f60162ba" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingOtherItemAmount_019b2283-de7d-776d-992b-f6fcee4a1eac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingOtherItemAmount"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-de7d-79aa-8444-de3eda813570" xlink:to="loc_us-gaap_SegmentReportingOtherItemAmount_019b2283-de7d-776d-992b-f6fcee4a1eac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019b2283-de7d-7218-9a14-01eb88c0a65d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-de7d-79aa-8444-de3eda813570" xlink:to="loc_us-gaap_Revenues_019b2283-de7d-7218-9a14-01eb88c0a65d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019b2283-de7d-73a6-97f1-a7b715b32370" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2283-de7d-79aa-8444-de3eda813570" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019b2283-de7d-73a6-97f1-a7b715b32370" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
