a form that calculates a total price

How can I create a form which through receiving a given kind of service, for a given number of hours, for a given cost/hour, already calculates the total my client will pay integrated to their payment form of choice?

Hello,

You can set calculations on your form in order to return such results.

You can check this guide to know about setting calculations on your form: https://www.jotform.com/help/301-How-to-Assign-Calculation-Value

Please check these guides as well in order to know how to set and assign fields in your form to be used as formulas to run your calculation: 

http://www.jotform.com/help/259-How-to-perform-calculation-in-the-form 

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

If you need assistance for proper guidance on this, you can share with us a specific form you're working on and we can assist you in helping you achieve the results to the form you're working on.

Thanks.