The “ISNUMBER” function relates to a group of functions called the “IS” functions. These validate if the contents are of a specific type or returned something, like the “ISERROR” or “ISBLANK” functions.


It follows a simple pattern.

  1. Value to check



will return 


Let’s see what happens when we try a string that is a number:


will return 


The validation is done by type, not the content of that type. In the example above, although the string’s content is a number, the value provided is a string, so it doesn’t even check the parameter’s value.

If we validate a “number” column.


will return


Same rationale as before. Since it’s a number column, the type is a number, so it’s fine. The same happens if the value is a floating-point number like ”3.14”.


You cannot use this function to check if a column’s contents or specific string values are numbers. You need to convert the string to a number and then compare it since SharePoint won’t covert the types for you.

On a personal note, I wish that it would convert the type automatically. It would make the function a lot more useful. Now, if we’re converting to a number and it doesn’t return an error, then we are sure it’s a number, so we don’t need to check it.


  1. Don’t use the “ISNUMBER” function to test anything other than numbers. It will return false even if the value is a number.
  2. Don’t nest it. There’s no real reason to do it, but if you find yourself in a situation where you have nested “IS” functions in a formula, you should review it and make everything more straightforward.
  3. Please note that formulas may have localization-based differences. For example, you should write “aaa” with “separating each of the arguments, but if your regional settings are set to Portugal, you should use “;” instead.


Microsoft’s IS Function Reference

Introduction to SharePoint formulas and functions

Back to the SharePoint’s list formula reference.

Photo by James Homans on Unsplash

Manuel Gomes

I'm a previous Project Manager, and Developer now focused on delivering quality articles and projects here on the site. I've worked in the past for companies like Bayer, Sybase (now SAP), and Pestana Hotel Group and using that knowledge to help you automate your daily tasks

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