Best math classes in Erode How to calculate Percentage? Percentages are a way of showing a part of a whole as a fraction of 100. It's often used to describe how much of something is present or how much something has changed. Formula : Percentage formula = (Value/Total value) × 100 For example, if you have 50 out of 100 marbles, that can be written as, Percentage = (50/100)* 100 = 50% We can write percentages as decimals or fractions, like 0.6% or 0.25%. In school, teachers use percentages to tell us how well we did on a test or exam. For example, if Raj got 78% in his final exam, it means he got 78 out of 100 marks. This percentage is calculated by adding up all of Raj's marks in all his subjects, then dividing by the total possible marks.