How to calculate a percentage
A percentage of a number is the number times the percentage divided by 100. To find what percent one number is of another, divide the part by the whole and multiply by 100.
Skip the maths and use the percentage calculator
The formula
Part = whole × percent ÷ 100. Percent = part ÷ whole × 100. Change = (new − old) ÷ old × 100.
Step by step
- Decide which of the three cases you have.
- Write down the whole, the part or the old and new values.
- Apply the matching formula.
- Check the answer looks sensible against 10% of the same number.
Worked example
15% of 240, and 36 as a percentage of 240
- 240 × 15 ÷ 100 = 36
- 36 ÷ 240 × 100 = 15
15% of 240 is 36, and 36 is 15% of 240.