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.
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