How to add 3 percent to user defined total field?

I am using the stripe payment system and user-defined amount.  However, I need to add 3% to the total amount.  I have tried using conditions but I cannot get it to work.  Please help.  I want to get this to work before I purchase the software.  

Thanks

Here's what you can do:

1). Remove the condition that calculates 3%

2). Add a form calculation widget http://widgets.jotform.com/widget/calculation

3). Add the Amount USD * .03 in the calculation.

ex.

4). Last is assign "Total + 3%" field as your total field in your Stripe payment.

ex.

Check my sample screencast here:

I hope that helps. Let us know if you have any questions or if you need further assistance.