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 FileMaker Pro Custom Functions

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ConvertFractToNum ( number )

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  Average rating: 4.5  (32 votes)
  Discuss this Custom Function

Colin Keefe, IT Solutions Consulting, Inc

Converts a fraction to a real number.

Sample Input:
ConvertFractToNum(5 1/2)
Sample Output:

 Then copy & paste into FileMaker Advanced's Edit Custom Function window.

Click here to copy To Clip Manager if you have myFMbutler's Clip Manager installed


I've been using Mikhail Edoshin's Fraction() custom function for awhile now - it's great. (see:

For a particular application, I needed a method to convert user-entered fractions back into a real number, so I could perform math on it, so I wrote this up to complement Mikhail's function. Feed it a fraction, and it'll do its level best to produce a real number.

There's some room for improvement here in terms of error capture, but much of that could be handled at field-level validation, to prevent malformed fractions from being entered.

Note: these functions are not guaranteed or supported by Please contact the individual developer with any questions or problems.

This is my Custom Function and I want to edit it


This is handy, but doesn't correctly handle fractions without a space (e.g. "1/2"). I've modified it a bit:

Let ( [
$number = Trim(number);
$integer = LeftWords($number;1);
$denominator = Right ( $number ; Length($number)-Position($number; "/";1;1 ));
$numerator = Middle ( $number ; Position ( $number ; " "; 1 ; 1 ) ; Position ( $number ; "/"; 1 ; 1 )-Position ( $number ; " "; 1 ; 1 ) )

// no slash, so no fraction

// no space, so no valid fraction
PatternCount($number;" ")=0;$numerator/$denominator;

// too many spaces, so no valid fraction
PatternCount($number;" ")>1;$number;

// - we have a fraction to parse
$integer + ($numerator/$denominator)

Sam Barnum, 360Works
November 16, 2010 11:48am

Is there a way to use this with negative fractions? Say I have -2 4/8
right now it returns 2.5 when i would like it to return -2.5

Any help would be appreciated.


Matt, Calgary
August 16, 2012 10:14pm

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