I have a switch at the top of my page that is millimeters or inches.

I have a switch at the top of my page that is millimeters or inches. (mm by default)

Then I have a list of a bunch of measurements. I am trying to add the code so that clicking the Inches on the switch divides all measurement values by 25.4. But I always get a value of 0.000 when I do this.

Example code:

IF Units IS EQUAL TO "Inches"

INSERT {Pitch}/25.4 INTO Pitch

How do I make this work?

I see that you are using the same field to perform calculation and inset the result:

Please create another field and try copying the results into that field.

Here is my cloned form: https://form.jotform.com/93392211073956