Percentage Calculator
Free percentage calculator. Work out what percent of a number, what percentage one number is of another, percentage increase or decrease, and add or subtract a percentage.
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What it does
A percentage is a fraction written out of a hundred. Every question on this page is the same division dressed differently: a part, a whole, and the ratio between them. The four boxes cover the four ways people actually ask it — how much is a slice, how big is a slice, how much did something move, and what is the price after the discount.
How to use it
- Pick the box that matches your question. They work independently.
- Type the two numbers. A comma decimal separator works as well as a dot.
- The answer appears as you type — there is no button to press.
The arithmetic runs in your browser. Nothing you type is sent anywhere and nothing is stored, so you can use these with real numbers.
Frequently asked questions
How do I calculate a discount?
Use the last box: type the original price, choose Subtract, and type the discount percentage. It shows both the amount taken off and the final price.
Why is percentage change from zero undefined?
Percentage change divides the difference by the starting value. If you started at zero there is nothing to divide by, and going from 0 to anything is an infinite increase — so the honest answer is that the question has no number.
Is a 50% rise followed by a 50% fall back to where it started?
No. 100 rises to 150, then falls by half of 150, which is 75. Percentages compound on whatever the current value is, not on the original — which is why a stock that halves needs to double to recover.
What happens with negative numbers?
Percentage change uses the size of the starting value, ignoring its sign. Going from -100 to -50 is shown as a 50% increase, because the number got bigger. Tools that skip this show it as a decrease, which reads backwards.
Wikipedia — Percentage
Wikipedia — Percentage point
Wikipedia — Relative change
Wikipedia — Discounting