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.
Unfortunately it is currently not possible to achieve your requirement.
Please be noted that calculated amount can only be passed to payment question if you have set it to as "Collect Donations/Custom Amount Payments". It will always be a one time payment.
Calculated amount/ custom payment cannot be used for recurring or subscription payments. You will actually have to add the subscription products in your PayPal payment question with fixed price.
Hope this answers your query.
Do get back to us if you have any questions.