Percentage calculator

How do I calculate a percentage of a number?

To find X% of a number Y, multiply Y by X and divide by 100. For example, 15% of 200 = (200 × 15) ÷ 100 = 30. Or simply move the decimal point: 10% of any number is that number divided by 10. For 15%, calculate 10% and add half of that. Mental maths shortcuts like these are faster than reaching for a calculator for common percentages.

How do I calculate a percentage increase or decrease?

Percentage change = ((New Value − Old Value) ÷ Old Value) × 100. If a price goes from $80 to $100, the increase is ((100 − 80) ÷ 80) × 100 = 25%. If it goes from $100 to $80, the decrease is ((80 − 100) ÷ 100) × 100 = −20%. Note that a 25% increase followed by a 20% decrease does not return you to the original number.

What is the difference between percentage points and percent?

This is a commonly confused distinction. If an interest rate rises from 2% to 3%, it has increased by 1 percentage point — but it has increased by 50% (because 3 is 50% more than 2). Percentage points measure absolute change; percent measures relative change. Politicians and media often use these interchangeably, which can be misleading.

How do I work out what percentage one number is of another?

Divide the first number by the second and multiply by 100. For example, to find what percentage 45 is of 180: (45 ÷ 180) × 100 = 25%. This is useful for calculating test scores, profit margins, discount amounts, and many everyday situations. Use the second tab of this calculator for a quick result.