How can we sell products and also collect a custom amount?

I've now read a whole bunch of comments here and elsewhere and still can't find the solution to our problem, which is quite simple: We're a PTA. Membership is $10/year. In some families, both parents join; in others only one. In either case, that's a "product" with a fixed cost of $10/unit. BUT we also depend on contributions, which by definition are variable.For the life of me, I can't figure out a way to accommodate both in my JotForm using Square. My choices are to "sell products" (at fixed prices) OR to accept "contributions" (in amounts established by the payor) -- but NOT BOTH?! The utility of the JotForm/Square "integration" is for me extremely limited if that's the case, so I hope someone will show me what I'm missing. Thanks!

To allow for collecting using both products and a variable amount, set up your options outside of the payment field using regular fields like single/multiple choice, number fields etc.  For options without numeric values, it is possible to assign those options calculation values:

https://www.jotform.com/help/301-How-to-Assign-Calculation-Value

Once you have assigned values, a calculation field can be used to get the total and/or perform further calculations:

https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget

That total can be passed along to the payment field for payment:

https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field

Thank you, David! That solved my problem.

For whatever it's worth, below is a screen shot of that portion of the form. I also set the Square credit card payment field as conditional: It only shows up if the user checks the "pay by credit card" box.

One thing I'm still not clear on, though, is whether there's a way to "protect" the Total Payment field from user entry. Although the Form Calculation widget puts the correct total for PTA memberships and Cougar Contribution in the TOTAL PAYMENT box, it appears that this can be modified, overriding the calculated amount, which is not a good thing.

Here is how you can make the result field read-only:

Which I did in your form already. So please check and let us know how it worked.

Thank you!

Wow, that was easy! Thank you, Nik!