Percentage Calculator
Answer the four percentage questions people actually ask. Type your numbers into the sentence that matches and the result, with its working, appears instantly.
- Runs in your browser
- No sign-up
- Free to use
Percentage of a number
One number as a percentage of another
Percentage change
Increase or decrease by a percentage
How to use Percentage Calculator
- Find the sentence that matches your question, for example “What is 15% of 240?”.
- Type your numbers into the blanks.
- Read the answer next to it; it updates as you type.
- Check the formula line underneath to see how the result was worked out.
Percentage Calculator features
Four calculators on one page
Percentage of a number, one number as a percentage of another, percentage change, and increase or decrease by a percentage.
Written as plain questions
Each calculator is a sentence with blanks, so there is no guessing which box means what.
Working shown
The formula with your own numbers is displayed under every result.
Live results
No button to press; answers update on each keystroke.
Handles decimals and negatives
Works with fractional percentages and with values that go down as well as up.
When to use Percentage Calculator
- Working out a discount, tip, tax or commission.
- Converting a test score into a percentage.
- Measuring growth or decline between two figures, such as sales or prices.
- Applying a pay rise or a price increase to an existing amount.
Percentage Calculator FAQ
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 240 is 240 × 15 ÷ 100 = 36.
How do I work out percentage change?
Subtract the old value from the new value, divide by the old value and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25% increase.
Why is a 50% increase followed by a 50% decrease not the original number?
Because each percentage applies to a different base. 100 increased by 50% is 150; 150 decreased by 50% is 75. The decrease is taken from the larger number.
What is the difference between percent and percentage points?
Percentage points measure the simple difference between two percentages. A rate rising from 4% to 6% is up 2 percentage points, but that is a 50% increase in the rate.
Can the result be more than 100%?
Yes. 250 is 250% of 100, and a value that triples has increased by 200%.
Percentages in one idea
Per cent means “per hundred”. Saying 15% is another way of writing the fraction 15/100, or the decimal 0.15. Every percentage problem is that one relationship between three quantities, a part, a whole and a rate, with a different one missing. Find the part when you know the rate and the whole; find the rate when you know the part and the whole.
The most common mistake is using the wrong whole. A percentage change is always relative to the starting value, not the ending one, which is why a rise from 50 to 100 is 100% but a fall from 100 to 50 is 50%. When comparing prices, discounts or statistics, check what the percentage is “of” before drawing a conclusion.
Percentages also hide the size of what they describe. A risk that rises by 50% sounds alarming, but if it goes from two in a million to three in a million the change is tiny in absolute terms. Reporting both the percentage and the actual numbers avoids that trap. The same applies to small samples: when three out of four people agree, “75%” suggests a precision that four answers cannot support. A useful habit is to ask “of how many?” whenever a percentage is used to make a point.