Percentage Calculator
Work out a percentage of a number, what percent one number is of another, or the percentage change between two numbers. Every answer shows the working.
15% of 200
30
- 200 plus 15%
- 230
- 200 minus 15%
- 170
15% of 200 is 30. Adding it gives 230; taking it off gives 170.
How it's worked out
- Turn the percentage into a decimal
15 ÷ 1000.15 - Multiply by the number
0.15 × 20030
- 15% part3015%
- The rest17085%
How percentages work
A percentage is a number out of 100. "15%" means 15 for every 100, which is the decimal 0.15. Every percentage question comes down to one of three formulas.
X% of Y = X ÷ 100 × Y
X as a % of Y = X ÷ Y × 100
% change from X to Y = (Y − X) ÷ X × 100
Worked example: a sale price
A jacket costs 4,500 and is 30% off. 30% of 4,500 is 0.30 × 4,500 = 1,350, so you pay 4,500 − 1,350 = 3,150. Pick "X% of a number" above and the calculator shows both the plus and minus figures.
Percentage change versus percentage points
If a tax rate moves from 5% to 6%, it has risen by 1 percentage point, but by 20% in relative terms, because (6 − 5) ÷ 5 × 100 = 20. News reports often mix the two up.
Questions people ask
How do I work out a percentage of a number?
Divide the percentage by 100 and multiply by the number. 15% of 200 is 0.15 × 200 = 30.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. 30 out of 120 is 30 ÷ 120 × 100 = 25%.
How is percentage change calculated?
Subtract the old value from the new one, divide by the old value, and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = a 25% increase.
Why isn't a 20% rise undone by a 20% fall?
Each percentage is taken of a different starting number. 100 plus 20% is 120, but 120 minus 20% is 96, because the 20% is now taken from 120.
About this calculator
Formula and rules last checked 25 October 2026Written and tested by the CalculatorDex teamReport a problem