Calculated Fields for ACF supports formatting the formula output using a format string. The format string is passed to the PHP sprintf() function. So any format string that works with that function also works with this plugin. The format string is entered into the "Number format" in the field definition:
The PHP formatting string consists of five different segments (well, actually six but in the case of this plugin, only five of them matters), percent sign, flags, width, precision, and type specifier put together like this:
Percent sign %
The percent sign marks the beginning of a number format string. It always needs to be there to mark the beginning of a rule to format a number.
The flags are used to pad the resulting output if needed. It can tell you how to pad (left or right justify) and what character to use, usually zeros or spaces. The flags often only make sense if you also use the width described below.
The minimum width of the resulting outputted string. You can use this to force the output to always have the same string length.
The number of decimals to use when the type is a floating-point number. You can use this to force a fixed number of decimals in the output.
The specifier defies how to treat the number. Typically the most used values would be "d" for a normal integer and "F" for a floating-point number.
Read the full details about the different parts and how to combine them in the PHP documentation.
Sometimes the easiest way to explain something is to use examples. Here are a few common format strings that you may find useful:
|%d||12||12||Convert the input to an integer.|
|%5d||12||12||Like above. Pad the result with spaces so that the total output is 5 characters wide.|
|%05d||12||00012||Like above, but pad using zeros.|
|%F||12.123||12.123000||Convert the input to a floating-point number with 6 decimal places.|
|%0.2F||12.12345||12.12||Like above, but with two decimal places.|
|%0.2F||12||12.00||Like above, not that there are always two decimal places.|
|$%0.2F||12||$12.00||Note that anything before the percent sign will be outputted "as is". This can be used to add a currency symbol.|
|%0.2F SEK||12||12.00 SEK||Like above, but with additional characters after the type specification. These are also outputted as is.|
It’s also possible to omit output if the formula returns zero (0). To do this, toggle the "Blank if zero" field to Yes.