Percentage Calculator
The essential percentage calculator — find X% of a number, work out what percentage one number is of another, or calculate the percentage change between two values. Full step-by-step working shown for every calculation.
20% of 150
30
How it works
Convert the percentage to a decimal
Divide the percentage by 100 to get the decimal multiplier: 20% = 0.2.
Result:0.2Multiply by the number
Multiply the decimal by 150: 0.2 × 150 = 30.
Result:30
Key percentage formulas
Worked examples
What is 15% of 80?
- 1Convert %: 15 ÷ 100 = 0.15
- 2Multiply: 0.15 × 80 = 12
30 is what percentage of 120?
- 1Divide: 30 ÷ 120 = 0.25
- 2Multiply by 100: 0.25 × 100 = 25%
What is the % change from 80 to 100?
- 1Difference: 100 − 80 = 20
- 2Divide by original: 20 ÷ 80 = 0.25
- 3Multiply by 100: 0.25 × 100 = 25%
Frequently asked questions
How do you calculate a percentage of a number?+
Divide the percentage by 100 and multiply by the number. E.g., 20% of 150 = (20/100) × 150 = 30.
How do you calculate percentage change?+
Percentage change = ((new value − original value) / original value) × 100. A positive result is an increase; negative is a decrease.
How do you find what percentage one number is of another?+
Divide the part by the whole, then multiply by 100. E.g., 30 is what % of 150? (30/150) × 100 = 20%.
What does percent mean?+
"Per cent" means "per hundred". So 45% means 45 out of every 100, or 45/100 = 0.45 as a decimal.
How do you work out a reverse percentage?+
If a value after a percentage change is known, divide by (1 ± the percentage as a decimal) to find the original. E.g., after a 20% increase the price is £120: original = 120 / 1.2 = £100.
How do you convert a percentage to a decimal?+
Divide by 100. E.g., 35% = 35/100 = 0.35.