<?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>0001450678</rptOwnerCik>
            <rptOwnerName>RAMLO RANDY A.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>118 SECOND AVENUE SE</rptOwnerStreet1>
            <rptOwnerStreet2>P.O. BOX 73909</rptOwnerStreet2>
            <rptOwnerCity>CEDAR RAPIDS</rptOwnerCity>
            <rptOwnerState>IA</rptOwnerState>
            <rptOwnerZipCode>52407-3909</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President/CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</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>88</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1874</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 not distributed 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/ Randy A. Ramlo 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
0001450678
RAMLO RANDY A.
118 SECOND AVENUE SE
P.O. BOX 73909
CEDAR RAPIDS
IA
52407-3909
1
1
0
0
President/CEO
Common Stock
2015-03-26
4
J
0
88
0
A
1874
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 not distributed 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/ Randy A. Ramlo by Michael T. Wilkins, Attorney-in-Fact
2015-03-27