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Mod

Returns the remainder after dividing the first number by the second. Runtime-proven on a live Marketing Cloud Engagement CloudPage — including the sign rule and the NaN result for a zero divisor.

Next
Runtime verified Test scripts included

Syntax

Mod(dividend, divisor)  →  number
2 arguments — exactly

Parameters

Name Type Required Description
dividend string | number Yes Number to divide
divisor string | number Yes Number to divide by

Example

%%[
  VAR @rest
  SET @rest = Mod(10, 3)
]%%
Remainder: %%=v(@rest)=%%

Renders Remainder: 1.

The common use is bucketing — pair it with Random or a subscriber ID to split an audience into groups:

%%[
  VAR @bucket
  SET @bucket = Mod(AttributeValue("SubscriberID"), 4)
]%%

@bucket is 0, 1, 2 or 3. Note that a negative dividend gives a negative bucket, so normalise first when the ID can be negative.

Return value

number — the remainder after dividing the first number by the second.

The result takes the sign of the dividend, and a divisor of 0 yields NaN instead of raising an error. NaN is an IEEE numeric value rather than a status token, so there is no closed literal set to match against.

Behaviour

Basic remainders. Mod(10, 3) gives 1, Mod(500, 12) gives 8, and a dividend smaller than the divisor returns the dividend unchanged: Mod(3, 10) gives 3.

Decimal operands are accepted. Mod(10.5, 3) gives 1.5 and Mod(10, 3.5) gives 3. A worked decimal case matched the official example exactly: Mod(-500.123, 12.456) renders -1.88300000000001.

Numeric strings are accepted. Mod("10", "3") gives 1, Mod(10, "3") gives 1, and Mod("10.5", "0.25") gives 0.

Non-numeric input aborts the page. A non-numeric string (Mod("abc", 3)), a boolean-like string (Mod("true", 3)), and a date value (Mod(Now(), 3)) each abort the CloudPage with HTTP 422, discarding all output rendered before the call.

The sign follows the dividend

The official page does not say which operand decides the sign of the remainder, and languages genuinely disagree about it. At runtime, the sign always follows the first argument:

Call Result
Mod(10, 3) 1
Mod(-10, 3) -1
Mod(10, -3) 1
Mod(-10, -3) -1

That is truncated-remainder behaviour, matching C and JavaScript’s %, and the opposite of the floored modulo used by languages such as Python. If you are porting an expression from a floored-modulo language, negative dividends will give you a different answer — normalise explicitly when you need a non-negative remainder. See the finding on Differs from official docs.

Dividing by zero

Mod does not abort on a zero divisor. It renders the three ASCII characters NaN in every case — Mod(10, 0), Mod(-10, 0), and Mod(0, 0) all produce NaN, including the non-zero-dividend case.

This is where Mod and its sibling Divide part ways: Divide renders ∞ for a non-zero dividend and only falls back to NaN for 0 / 0. Code that tests for one sentinel will silently miss the other, so guard the divisor rather than pattern-matching the result. Both are catalogued on Differs from official docs.

Show test script
%%[
  VAR @b
  SET @b = RequestParameter("b")

  /* sign rule: all four cases are safe and can share one request */
  IF @b == "mods" THEN
    OutputLine(Concat("Mod(10,3)=[", Mod(10,3), "]"))
    OutputLine(Concat("Mod(500,12)=[", Mod(500,12), "]"))
    OutputLine(Concat("Mod(3,10)=[", Mod(3,10), "]"))
    OutputLine(Concat("Mod(-10,3)=[", Mod(-10,3), "]"))
    OutputLine(Concat("Mod(10,-3)=[", Mod(10,-3), "]"))
    OutputLine(Concat("Mod(-10,-3)=[", Mod(-10,-3), "]"))
  ENDIF

  /* decimal operands */
  IF @b == "moddec" THEN
    OutputLine(Concat("Mod(-500.123,12.456)=[", Mod(-500.123,12.456), "]"))
    OutputLine(Concat("Mod(10.5,3)=[", Mod(10.5,3), "]"))
    OutputLine(Concat("Mod(10,3.5)=[", Mod(10,3.5), "]"))
  ENDIF

  /* numeric strings */
  IF @b == "modstr" THEN
    OutputLine(Concat("Mod('10','3')=[", Mod("10","3"), "]"))
    OutputLine(Concat("Mod(10,'3')=[", Mod(10,"3"), "]"))
    OutputLine(Concat("Mod('10.5','0.25')=[", Mod("10.5","0.25"), "]"))
  ENDIF

  /* zero divisor: does NOT abort, so all cases can share one request */
  IF @b == "m0" THEN
    OutputLine(Concat("Mod(10,0)=[", Mod(10,0), "]"))
    OutputLine(Concat("Mod(-10,0)=[", Mod(-10,0), "]"))
    OutputLine(Concat("Mod(0,0)=[", Mod(0,0), "]"))
    /* contrast: Divide renders the infinity symbol here */
    OutputLine(Concat("Divide(10,0)=[", Divide(10,0), "]"))
  ENDIF

  /* each risky branch aborts the page: the start marker never renders */
  IF @b == "fewm" THEN
    OutputLine(Concat("--- fewm start ---"))
    OutputLine(Concat("Mod(1)=[", Mod(1), "]"))
  ENDIF

  IF @b == "manym" THEN
    OutputLine(Concat("--- manym start ---"))
    OutputLine(Concat("Mod(1,2,3)=[", Mod(1,2,3), "]"))
  ENDIF

  IF @b == "strm" THEN
    OutputLine(Concat("--- strm start ---"))
    OutputLine(Concat("Mod('abc',3)=[", Mod("abc",3), "]"))
  ENDIF

  IF @b == "boolm" THEN
    OutputLine(Concat("--- boolm start ---"))
    OutputLine(Concat("Mod('true',3)=[", Mod("true",3), "]"))
  ENDIF

  IF @b == "datem" THEN
    OutputLine(Concat("--- datem start ---"))
    OutputLine(Concat("Mod(Now(),3)=[", Mod(Now(),3), "]"))
  ENDIF
]%%

Availability

Platform Available
Marketing Cloud Engagement Yes
Marketing Cloud Next Yes, from API 67.0

See also