How to use the percentage calculator
- 1Choose the kind of percentage sum you need.
- 2Enter the numbers.
- 3Read the result.
Percentage formulas
- 01X% of a number = percentage ÷ 100 × number
- 02X is what % of Y = X ÷ Y × 100
- 03% change from X to Y = (Y − X) ÷ X × 100
"Per cent" means "per hundred". To take a percentage of a number, turn the percent into a fraction (divide by 100) and multiply: 20% of 500 is 0.2 × 500 = 100.
To find what percentage one number is of another, divide the first by the second and multiply by 100: 500 is 20% of 2,500. And to find a percentage change, take the difference, divide by the starting value, and multiply by 100 — a rise from 2,000 to 2,500 is a 25% increase.
Percentage example
20% of 500 is 100.
Good to know
- To find 10% of a number, drop the last digit (10% of 450 is 45); 5% is half of that.
- A percentage increase then the same percentage decrease does not return to the start.
- For percentage change, divide by the starting value, not the ending one.
Percentage calculator — common questions
How do I find a percentage of a number?
Divide the percentage by 100 and multiply by the number. 20% of 500 is 0.2 × 500 = 100.
How do I find what percent one number is of another?
Divide the first number by the second and multiply by 100. 500 out of 2,500 is 20%.
How do I calculate percentage increase or decrease?
Subtract the old value from the new, divide by the old value, and multiply by 100. From 2,000 to 2,500 is a 25% increase.
Sources
- Percentage arithmetic — standard mathematics
Formulas last reviewed: September 30, 2026 ·How we check our formulas