Percentage Calculator
Work out a percentage of a number, find what percent one number is of another, or find the whole when you only know the part. Results update as you type.
What is X% of Y?
Example: what is 15% of 240?
X is what percent of Y?
Example: 45 is what percent of 180?
X is Y% of what number?
Example: 30 is 12% of what number?
How percentages work
"Percent" means "out of 100". So 25% is 25 out of every 100, which is the same as the fraction 25/100 or the decimal 0.25. Every percentage question involves three numbers: the part, the whole and the percentage. If you know two of them, you can find the third.
Percentage formulas
Part = Whole × (Percentage ÷ 100)
Percentage = (Part ÷ Whole) × 100
Whole = Part ÷ (Percentage ÷ 100)
Worked examples
| Question | Working | Answer |
|---|---|---|
| What is 15% of 240? | 240 × 0.15 | 36 |
| 45 is what percent of 180? | 45 ÷ 180 × 100 | 25% |
| 30 is 12% of what number? | 30 ÷ 0.12 | 250 |
| What is 12.5% of 80? | 80 × 0.125 | 10 |
Quick mental maths
- 10%: move the decimal point one place left. 10% of 360 is 36.
- 5%: take 10% and halve it. 5% of 360 is 18.
- 15%: add 10% and 5%. 15% of 360 is 54.
- 1%: move the decimal point two places left. 1% of 360 is 3.6.
- 50% is half, and 25% is half of a half.
Common mistakes
- Mixing up percent and percentage points. If a rate rises from 4% to 6%, it went up by 2 percentage points, but that is a 50% increase.
- Using the wrong total. "What percent of the total" needs the total on the bottom of the fraction, not the other part.
- Forgetting to divide by 100. To use a percentage in a calculation, convert it first: 8% becomes 0.08.
Frequently asked questions
How do I convert a percentage to a decimal?
Divide by 100, or move the decimal point two places to the left. 8% is 0.08 and 125% is 1.25.
Can a percentage be more than 100%?
Yes. 150% of 40 is 60. A value above 100% just means more than the whole you started with.
How do I work out a percentage of a total in a spreadsheet?
Divide the part by the total, for example =B2/B10, then format the cell as a percentage.
What number formats can I type?
Plain numbers such as 12.5, numbers with thousands commas such as 1,250.50, and a trailing % sign in the percentage boxes.
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Results are for general information only. The calculators are tested, but please double-check anything important before relying on it for financial, tax, legal or medical decisions.