Form - Data input and perform calculations

I’m new to Hugo but managed to get my site up and operational pretty quickly. Now I want to move another site to Hugo.

I need to take input from a couple of form fields and perform some calculations on the data and return it to the user. For instance, user inputs 10 into Field1 and 5 into Field2, I need to do something like field1 + field2 and return that data in html as 50.

I was doing this with PHP but I would like to get away from PHP. What is the best way to do this with Hugo? Javascript or some 3 party form service? Thanks is advance for your thoughts.

That one.