This is the simplest application that exists to calculate percentages, you simply have to enter the amount of which you want to calculate a percentage, be it an invoice, a mortgage, the value of a car, whatever you want. Then you choose a percentage between 1 and 100 and the app automatically calculates the percentage of the amount entered.

For example, you enter the value "200" and choose the percentage "10", the app immediately tells you that 10% of 200 is 20.