I'm doing a bit of math with AMPscript, and I'd like to be able to round a number DOWN

eg: I would like 5.5, 5.6, 5.7 etc.. to become 5, not 6

The standard FormatNumber() function will automatically round a number UP if the decimal point is greater than or equal to .5

I've tried finding a Floor() function or some option to FormatNumber() that will yield the rounded-down number, but I haven't had any luck finding a solution.

Does anyone have a suggestion for obtaining the floor value of a number?

4 Answers 4


You can still use FormatNumber-- just subtract 0.5 from the number before feeding it into FormatNumber. Something like this would probably work:

FormatNumber(@OriginalNumber-0.5, "N0", "en-US")

Since you subtract 0.5, a number such as 1.99 becomes 1.49 which would round down, while 2.49 would become 1.99 and round up.

  • Simple and elegant. Dec 2, 2014 at 0:41
  • Impressive. The force is strong with this one!
    – Timothy
    Dec 2, 2014 at 15:28
  • 1
    this works: Set @rounded = FormatNumber(Subtract(@OriginalNumber,.5), "N0", "en-US")
    – Snowalker
    Dec 7, 2017 at 14:36
  • @Snowalker's answer is correct. You have to use the subtract function in AMPscript. Jul 24, 2019 at 13:44

The other answers are ok, but I would like to add mine as it still uses FormatNumber and also supports negative numbers.

set @number = '4.500000001'
set @mod = Mod(@number, 1)

if @mod > .5 then 
    set @roundedDown = FormatNumber(Subtract(@number,1), 0)
elseif @mod < 0 AND @mod > -.5 then // handle negative values
    set @roundedDown = FormatNumber(Subtract(@number,1), 0)
    set @roundedDown = FormatNumber(@number, 0)

Original Value: %%=v(@number)=%%
<br />
Rounded Down: %%=v(@roundedDown)=%%

Another thought. You could use server side javascript instead of AMPscript, and just use math.floor.

  • This will certainly work in other scenarios, but my situation involves sending content in an email (through ExactTarget), so the javascript won't execute Dec 1, 2014 at 19:25
  • 1
    @ampersandre - Server Side Javascript is available to you in email sending. See help.exacttarget.com/en/documentation/exacttarget/content/… for more info. Use of SSJS in email sends is extremely useful, however, more in-depth data retrieval can slow down sending. MATH.floor would not cause any harm here. Dec 2, 2014 at 0:36

This may seem a little hack-ish, but I would do it like this.

SET @DynamicField1 = 127.35
SET @DynamicField2 = Substring(@DynamicField1, 1,  Subtract(IndexOf(@DynamicField1, "."), 1) )

@DynamicField2 now is the floor. Good luck

  • I changed 127.35 to 127.51 and it results into 127 instead of 128
    – Snowalker
    Nov 22, 2018 at 19:07

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