How it works
A percentage expresses a part of a whole as a fraction of 100. To find X% of a number, multiply the number by X and divide by 100: 20% of 250 = 250 × 20 / 100 = 50. To find what percent one number is of another, divide the part by the whole and multiply by 100.
Percentage change is calculated as (New − Old) / Old × 100. If a price rises from $200 to $250, that is a 25% increase. These formulas are used for discounts, raises, grades, interest, taxes and statistics.