You can create a Textbox field that only accepts numbers using the Format validation option set to the Numeric option. Or, you can use the Custom Mask option with #### as the Format Mask.
To convert this numeric value to a number:
Add a Calculation field set to the Number type – with zero decimals.
Set the calculation to:
=int32.parse(Text)Make sure to replace ‘Text’ with the name of the Textbox field on your form.
The Calculation field will automatically convert the numeric value from the Textbox field into a number.
You can then use this number in calculations.
Learn more in our Numeric calculations help guide.