Percentage calculator with three modes
This percentage calculator answers the three most common questions: what is X% of Y, X is what percent of Y, and the percent change from X to Y.
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How to use the percentage calculator
- Find the row for your question: X% of Y, X as a percent of Y, or the percent change from X to Y.
- Type your two numbers into that row's boxes. Decimals and negative numbers are fine.
- Press Calculate on the same row.
- Read the answer in the blue box under the row, written out as a full sentence.
How the percentage calculator works
A percentage is a fraction of 100: 20% means 20 out of every 100. Each of the three calculators rearranges that one idea for a different question, so you never have to remember which number to divide by which.
Results are shown with up to four decimal places and written as a sentence, such as "20% of 250 is 50", so you can copy the answer straight into a report or a message.
Formula
X% of Y = X ÷ 100 × Y. X as a percent of Y = X ÷ Y × 100. Percent change from X to Y = (Y − X) ÷ |X| × 100, where a positive answer is an increase and a negative one is a decrease.
Example
20% of 250 is 20 ÷ 100 × 250 = 50. Asked the other way round, 50 is 50 ÷ 250 × 100 = 20% of 250.
If a price rises from 200 to 250, the change is (250 − 200) ÷ 200 × 100, a 25% increase. If it then falls back from 250 to 200, the change is (200 − 250) ÷ 250 × 100, a 20% decrease. The two figures differ because each is measured from a different starting point.
Tips and common mistakes
Percent changes don't cancel out
A 50% fall needs a 100% rise to get back to where you started. Always check which value is the starting point.
Percentage points are not percent
An interest rate moving from 4% to 5% has risen by 1 percentage point, but the rate itself is 25% higher.
Adding and removing tax
To add 20% to 100, take 20% of 100 and add it, giving 120. To remove 20% from a price that already includes it, divide by 1.2 instead of subtracting 20%.
Use the right tool for loans
Loan interest compounds every month, so a simple percentage gives the wrong cost. Use the EMI calculator to see real repayments.
Tracking health goals
Working on your weight? Pair this tool with the BMI calculator to see how a change in kilograms moves your BMI.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12.
How do I work out a percentage increase?
Subtract the old value from the new one, divide by the old value and multiply by 100.
Why can't the starting value be zero?
Percent change divides by the starting value, and dividing by zero has no answer.
Can I use negative numbers?
Yes. Percent change uses the size of the starting value, so a move from −10 to −5 shows as a 50% increase.
Is 20% off and then 10% off the same as 30% off?
No. You pay 0.8 × 0.9 = 72% of the price, which is a total discount of 28%.