What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
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.
Unfortunately, it's currently not possible to do calculations using a matrix field because the field doesn't have the Calculation property which is required to perform calculations.
However, you can use regular fields and custom CSS code to emulate the matrix appearance and this way you will be able to perform calculations in your form.
If you have further questions, please let us know.