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.
You may calculate a total value based in your user's input or in a selection from a drop down, as well as from a selection in a check box or radio button.
Please take a look on this guide, you will find detailed info about it: http://www.jotform.com/help/259-How-to-perform-calculation-in-the-form.
Do let us know if you have questions, we will be glad to help you.