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<?xml version="1.0" encoding="windows-1252"?> |
<ownershipDocument> |
| <schemaVersion> X0306 </schemaVersion> |
| <documentType> 4 </documentType> |
| <periodOfReport> 2022-08-20 </periodOfReport> |
| <notSubjectToSection16> 0 </notSubjectToSection16> |
| <issuer> |
| | <issuerCik> 0001144215 </issuerCik> |
| | <issuerName> ACUITY BRANDS INC </issuerName> |
| | <issuerTradingSymbol> AYI </issuerTradingSymbol> |
| | </issuer> |
| <reportingOwner> |
| | <reportingOwnerId> |
| | | <rptOwnerCik> 0001302261 </rptOwnerCik> |
| | | <rptOwnerName> HOLCOM KAREN J </rptOwnerName> |
| | | </reportingOwnerId> |
| | <reportingOwnerAddress> |
| | | <rptOwnerStreet1> C/O ACUITY BRANDS, INC. </rptOwnerStreet1> |
| | | <rptOwnerStreet2> 1170 PEACHTREE STREET, NE, SUITE 2300 </rptOwnerStreet2> |
| | | <rptOwnerCity> ATLANTA </rptOwnerCity> |
| | | <rptOwnerState> GA </rptOwnerState> |
| | | <rptOwnerZipCode> 30309 </rptOwnerZipCode> |
| | | <rptOwnerStateDescription></rptOwnerStateDescription> |
| | | </reportingOwnerAddress> |
| | <reportingOwnerRelationship> |
| | | <isDirector> 0 </isDirector> |
| | | <isOfficer> 1 </isOfficer> |
| | | <isTenPercentOwner> 0 </isTenPercentOwner> |
| | | <isOther> 0 </isOther> |
| | | <officerTitle> SVP & Chief Financial Officer </officerTitle> |
| | | <otherText></otherText> |
| | | </reportingOwnerRelationship> |
| | </reportingOwner> |
| <nonDerivativeTable> |
| | <nonDerivativeTransaction> |
| | | <securityTitle> |
| <value> Common Stock </value> |
| </securityTitle> |
| | | <transactionDate> |
| <value> 2022-08-20 </value> |
| </transactionDate> |
| | | <transactionCoding> |
| <transactionFormType> 4 </transactionFormType> |
| <transactionCode> F </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| </transactionCoding> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 305 </value> |
| <footnoteId id="F1"/> |
| </transactionShares> |
| <transactionPricePerShare> |
| <value> 184.39 </value> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> D </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 16833 </value> |
| <footnoteId id="F2"/> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </nonDerivativeTransaction> |
| | </nonDerivativeTable> |
| <derivativeTable></derivativeTable> |
| <footnotes> |
| | <footnote id="F1"> The transaction(s) report(s) the withholding of stock to cover tax liability associated with the vesting of restricted stock or restricted stock units held by the reporting person. Such withholding is required under the Company's standard processes for such events. </footnote> |
| | <footnote id="F2"> The total direct shares owned includes 10,115 time-vesting restricted stock/units and 4 shares held in the employee stock purchase plan. </footnote> |
| | </footnotes> |
| <remarks></remarks> |
| <ownerSignature> |
| | <signatureName> Jill A. Gilmer, under Power of Attorney for Karen J. Holcom </signatureName> |
| | <signatureDate> 2022-08-23 </signatureDate> |
| | </ownerSignature> |
| </ownershipDocument> |