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# How to Use the DATA VALIDATION ISNUMBER Function in Excel

You can create your own data validation to allow numbers only in Excel. To do this, you need to use the ISNUMBER function. In this tutorial, you will learn how to create a data validation to allow only allow numbers using the ISNUMBER function.

## Use data validation in Excel to only allow numbers

### How to use the ISNUMBER Function in Excel for Data Validation

Data validation is a good practice to reduce issues during an audit. The data validation ISNUMBER function helps maintain this by allowing only number and date values. In the following example, you have two columns of values and results. The values column has data belonging to different types, and the result column shows whether the values are numbers. To do this:

• Go to cell B2.
• Insert the formula `=IF(ISNUMBER(B2),”Number”,""). `
• Click Enter
• Drag the formula to the cells B2 to B8 with your mouse.

This will show in column B whether the values in column A are numbers.

### Data Validation to Allow Numbers only

Using this logic, you can set a data validation rule that allows only numbers in a column. The following example uses a student data sheet. Column A has the names, column B has the classes, and Column C will have the ages. To limit column C to accept only number values:

1. Select cells C2:C6 by selecting cell C2 and dragging it till cell C6 with your mouse.
2. Go to Data > Data Validation.
3. Set Allow to Custom.
4. In the Formula field type the formula `=ISNUMBER(C2)`.
5. Click Ok.

This will set a data validation to allow numbers only in column C. Trying other data types will result in an error. You can set your own custom error message. To do this:

• After completing step 4, go to the Error Alert tab and set the Error Message to“Input not a number. Please enter a valid number.”
• Click Ok

If you try to enter a non-number in column C, Excel will show this message now.

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