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.
Are you using payment tools? Calculations are automatic on the payment tools, just enable the Total so you can see the total calculation on the form. Just click the payment field on your form and toggle the "Show Total" option on the top toolbar.
Or if you are using regular fields, you can use Form Calculation widget to get the total number of the selected fields. Form Calculation is under widgets.
We also have a complete guide about Form Calculation, https://www.jotform.com/help/259-How-to-perform-calculation-in-the-form
If you need further assistance, let us know here.