supereasy.toolsPercentage Calculator Online Free — X% of Y, % Change & More
Calculate any percentage instantly online: find X% of a number, work out what percentage one number is of another, or calculate the percentage increase or decrease between two values — free, no signup.
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How to calculate percentages online
Choose the calculation type using the tabs at the top, then enter your numbers. The result updates instantly as you type — no button to press.
The formula panel below the result shows exactly how the answer was calculated, so you can double-check the maths or explain it to someone else.
Three modes: 'X% of Y' finds a percentage of a number (e.g. 15% of 340 = 51); 'X is what % of Y' expresses one number as a fraction of another; '% change' calculates the increase or decrease between two values.
Frequently asked questions
- How do I find 15% of 340?
- Select the 'X% of Y' tab, enter 15 in the first field and 340 in the second. The result (51) appears immediately, along with the formula: 15 ÷ 100 × 340 = 51.
- How do I calculate a percentage increase or decrease?
- Select the '% change from X to Y' tab. Enter the starting value in X and the ending value in Y. A positive result means an increase; a negative result (shown with ▼) means a decrease.
- How do I work out what percentage one number is of another?
- Select the 'X is what % of Y' tab. Enter the part in X and the whole in Y. For example, to find what percentage 51 is of 340: enter 51 and 340 — the answer is 15%. The formula is (X ÷ Y) × 100.
- Can I use a percentage calculator online without downloading anything?
- Yes — this tool runs entirely in your browser. There is nothing to download or install and it works on any device, including mobile.
- Why is my percentage change showing a negative number?
- A negative percentage change means the value decreased. For example, going from 200 to 150 is a −25% change. Make sure you entered the original (starting) value in X and the new value in Y — swapping them will flip the sign.
- What is the formula for percentage change?
- Percentage change = ((New Value − Old Value) ÷ Old Value) × 100. A positive result is an increase; a negative result is a decrease. The formula panel below every result shows this calculation with your actual numbers.