JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
You can indeed apply calculation to field entries by using a calculation widget:
You would then add your fields into the calculation:
Depending on what the final result needs to be, you may need some parenthesis in there to separate out the values. For example if you want width x height then that number divided by the rest, your equation would need to be (width field * height field) / (144 * 12 * quantity field).
Here is your equation setup in a clone of your form:
You can clone my copy to see the full setup if you'd like:
If you have any further questions, let us know and we will be happy to help.