YourCal. Simply put, its your own calculator. This wonderful app is simple to use like all the other calculators but with the option of making 5 of your own formulas.
You can create 5 formulas and save them to use whenever you want. No hassle, no complicated ways to do basic equations that you need.
The app also has a very easy way of finding out percentages for you. Simply type in a number then hit the percentage tab to go on and click the amount you want to find!