Percentage Calculator
Three little questions cover almost every percentage problem you'll ever meet. Type your numbers and the answer appears instantly - with the sum written out underneath.
What is X% of a number?
X is what percentage of Y?
Percentage increase or decrease
How to work out percentages without a calculator
A percentage is just a fraction with 100 on the bottom - the word literally means "per hundred". Once that clicks, every percentage question becomes a short bit of multiplication or division:
- X% of a number: divide the percentage by 100, then multiply. So 15% of 240 is 0.15 × 240 = 36.
- One number as a percentage of another: divide the part by the whole and multiply by 100. 36 out of 240 is 36 ÷ 240 × 100 = 15%.
- Percentage change: take the difference, divide by the original value, multiply by 100. Going from 80 to 92 is (92 - 80) ÷ 80 × 100 = a 15% increase.
10% is easy - just move the decimal point one place. Build everything else from there: 5% is half of that, 1% is a tenth of it, and 15% is 10% plus 5%. So 15% of £240? 10% is £24, 5% is £12, answer £36. You'll be faster than the person reaching for their phone.
The mistake nearly everyone makes with percentage change
Percentage changes are not symmetric. If a £100 item rises 50% it costs £150 - but a 50% fall from £150 takes you to £75, not back to £100. The base changes each time, which is why a stock that drops 50% needs to gain 100% just to break even. Whenever a headline says something "fell 30% then recovered 30%", it hasn't recovered.
Percentage points vs percentages
If interest rates move from 4% to 5%, that's a rise of one percentage point - but a 25% increase in the rate itself. News reports mix these up constantly. Our third calculator above gives you the true percentage change between any two values.
Where you'll use this next
Most real-world percentage questions come with money attached. If you're checking a sale price, our discount calculator handles single and stacked reductions in one go; if you're adding tax to an invoice, the VAT calculator applies the correct UK rates; and if you're splitting a restaurant bill, the tip calculator does the percentage and the division together.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 to turn it into a decimal, then multiply by the number. For example, 22% of 350 is 0.22 × 350 = 77. The first calculator on this page does exactly this and shows the working.
How do I work out what percentage one number is of another?
Divide the part by the whole, then multiply by 100. If you scored 42 out of 60 on a test, that's 42 ÷ 60 × 100 = 70%.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide the result by the original value, and multiply by 100. A positive answer is an increase, negative is a decrease. Always divide by the original figure, not the new one.
How do I add or subtract a percentage from a number?
To add 18% to a price, multiply by 1.18. To reduce a price by 18%, multiply by 0.82. Multiplying by (1 + rate) or (1 - rate) is quicker and less error-prone than working out the percentage separately and adding it on.
Can a percentage be over 100?
Yes. 250% of 40 is 100, and a value that triples has increased by 200%. Percentages above 100 simply mean "more than the whole" - common when comparing growth over time.