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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-09-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001203171</rptOwnerCik>
            <rptOwnerName>RIFE JOHN 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>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-09-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>E</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>59</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>28.49</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8333</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote #1</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2014-09-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>11.999</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>28.49</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>11.999</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1721.229</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Shares acquired through participation in Issuer's dividend reinvestment program.</footnote>
        <footnote id="F2">The number of shares (excluding frationals) beneficially held indirectly by the Reporting Person includes: 6,545 shares held in an individual retirement account for Mr. Rife's benefit; 1,359 shares held individually by Mr. Rife's spouse; and 428 shares held in a SEP individual retirement account for Mr. Rife's benefit.</footnote>
        <footnote id="F3">Each share of phantom stock is the economic equivalent of one share of the Issuer's common stock. The shares of phantom stock become payable, in cash, in one lump sum or prorated overfive years, at the election of the Reporting Person, upon the Reporting Person's termination of service as a director.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ John A. Rife by Dianne M. Lyons, Attorney-in-Fact</signatureName>
        <signatureDate>2014-09-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
[{"type": "4", "sequence": "1", "filename": "wf-form4_141098693137196.xml", "description": "FORM 4", "secsgml_size_bytes": 6190}]
X0306
4
2014-09-15
0
0000101199
UNITED FIRE GROUP INC
UFCS
0001203171
RIFE JOHN A
118 SECOND AVENUE SE
P.O. BOX 73909
CEDAR RAPIDS
IA
52407-3909
1
0
0
0
Common Stock
2014-09-15
5
J
0
E
59
28.49
A
8333
I
See footnote #1
Phantom Stock
2014-09-15
4
A
0
11.999
28.49
A
Common Stock
11.999
1721.229
D
Shares acquired through participation in Issuer's dividend reinvestment program.
The number of shares (excluding frationals) beneficially held indirectly by the Reporting Person includes: 6,545 shares held in an individual retirement account for Mr. Rife's benefit; 1,359 shares held individually by Mr. Rife's spouse; and 428 shares held in a SEP individual retirement account for Mr. Rife's benefit.
Each share of phantom stock is the economic equivalent of one share of the Issuer's common stock. The shares of phantom stock become payable, in cash, in one lump sum or prorated overfive years, at the election of the Reporting Person, upon the Reporting Person's termination of service as a director.
/s/ John A. Rife by Dianne M. Lyons, Attorney-in-Fact
2014-09-17