<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-03-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000101199</issuerCik>
        <issuerName>UNITED FIRE GROUP INC</issuerName>
        <issuerTradingSymbol>UFCS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001626024</rptOwnerCik>
            <rptOwnerName>Helbing Kevin W.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>118 SECOND AVENUE SE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CEDAR RAPIDS</rptOwnerCity>
            <rptOwnerState>IA</rptOwnerState>
            <rptOwnerZipCode>52401</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Interim PFO/Asst VP/Controller</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common</value>
            </securityTitle>
            <transactionDate>
                <value>2015-03-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>85</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Issuer's Employee Stock Ownership Plan for self</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">This transaction represents an allocation of shares held in trust by the Issuer's Employee Stock Ownership Plan on behalf of the Reporting Person. Shares held in trust by the plan are notdistributed to the Reporting Person until retirement.</footnote>
        <footnote id="F2">Represents the approximate number of shares (excluding fractionals) allocated by the trustee/administrator of the Issuer's Employee Stock Ownership Plan for the Reporting Person's benefit.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Kevin W. Helbing by Michael T. Wilkins, Attorney-in-Fact</signatureName>
        <signatureDate>2015-03-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2015-03-26
0
0000101199
UNITED FIRE GROUP INC
UFCS
0001626024
Helbing Kevin W.
118 SECOND AVENUE SE
CEDAR RAPIDS
IA
52401
0
1
0
0
Interim PFO/Asst VP/Controller
Common
2015-03-26
4
J
0
20
0
A
85
I
By Issuer's Employee Stock Ownership Plan for self
This transaction represents an allocation of shares held in trust by the Issuer's Employee Stock Ownership Plan on behalf of the Reporting Person. Shares held in trust by the plan are notdistributed to the Reporting Person until retirement.
Represents the approximate number of shares (excluding fractionals) allocated by the trustee/administrator of the Issuer's Employee Stock Ownership Plan for the Reporting Person's benefit.
/s/ Kevin W. Helbing by Michael T. Wilkins, Attorney-in-Fact
2015-03-27