How to Calculate a Percentage (With Examples)
Learn how to calculate a percentage of a number, find what percent one number is of another, and convert between percentages, decimals and fractions.
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Frequently asked questions
How do I calculate a percentage of a number?
Convert the percentage to a decimal and multiply. 20% of 150 is 0.20 × 150 = 30.
How do I express one number as a percentage of another?
Divide the part by the whole and multiply by 100. 36 out of 40 is (36 ÷ 40) × 100 = 90%.
How do I find the original number from a percentage?
Divide the known amount by the percentage as a decimal. If 30 is 20%, the original is 30 ÷ 0.20 = 150.
What is a quick way to find 10%?
Move the decimal point one place to the left. 10% of 150 is 15, and you can scale from there — 5% is half of that, 20% is double.
How do I add a percentage to a number?
Multiply by (1 + the percentage as a decimal). Adding 8% to 50 is 50 × 1.08 = 54.
What does percent actually mean?
Percent means "per hundred", so 25% is 25 out of every 100, or the fraction 25⁄100, which equals 0.25.
The basics of percentages
A percentage is a number out of 100. To turn a part-of-a-whole into a percentage, divide the part by the whole and multiply by 100: percentage = (part ÷ whole) × 100. Scoring 36 out of 40 is (36 ÷ 40) × 100 = 90%.
Finding a percentage of a number
To find X% of a number, convert the percentage to a decimal and multiply. 20% of 150 is 0.20 × 150 = 30. The quick trick: 10% is just the number with the decimal moved one place, so 10% of 150 is 15, and 20% is double that.
Reverse percentages
If you know the percentage and the result, you can find the original. If 30 is 20% of a number, that number is 30 ÷ 0.20 = 150. This is handy for working out pre-discount prices or pre-tax amounts from a final figure.
Percentages appear everywhere — discounts, interest, tips, test scores and statistics — so a few mental shortcuts pay off. Remember that 50% halves a number, 25% quarters it, and 1% is the number divided by 100.
Results are estimates for general guidance in United Kingdom and may not reflect the latest local rates, fees or rules. Check official sources before making decisions.