# Data validation allow numbers only

=ISNUMBER(A1)

*Note: Excel has several built-in data validation rules for numbers. This page explains how to create a your own validation rule based on a custom formula.*

To allow only numbers in a cell, you can use data validation with a custom formula based on the ISNUMBER function.

In the example shown, the data validation applied to C5:C9 is:

=ISNUMBER(C5)

### How this formula works

Data validation rules are triggered when a user adds or changes a cell value.

The ISNUMBER function returns TRUE when a value is numeric and FALSE if not. As a result, all numeric input will pass validation.

Be aware that numeric input includes dates and times, whole numbers, and decimal values.

*Note: Cell references in data validation formulas are relative to the upper left cell in the range selected when the validation rule is defined, in this case C5.*

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