How do I find what percent one number is of another?

Divide the part by the whole and multiply by 100. For example, 30 is (30 ÷ 120) × 100 = 25% of 120.

How is percent change calculated?

Subtract the old value from the new value, divide by the old value, and multiply by 100. A price rising from $50 to $75 is a 50% increase.

Is my data sent anywhere?

No. All calculations happen in your browser. Nothing you enter is uploaded, stored, or shared.

Percentage Calculator

Solve any percentage problem in seconds. X% of Y, ratios, and percent change.

Percent (X)

Value (Y)

Result

Enter both values to see the result…

Everything is calculated instantly in your browser. Nothing is sent or stored anywhere.

About this tool

Percentage math shows up everywhere, sale prices, tips, grades, loan rates, and business metrics. This free percentage calculator handles the three calculations people actually need: finding X% of a number, figuring out what percentage one number is of another, and measuring the percent change between an old and new value.

Switch modes with one tap and the answer updates as you type, with the exact formula displayed beneath the result so you can see how it was computed. Common pitfalls are handled gracefully: dividing by zero or computing a percent change from zero shows a clear explanation instead of a confusing error.

How to use the percentage calculator

1Pick a mode: X% of Y, X is what % of Y, or % change.
2Enter your two numbers.
3Read the answer instantly, with the exact formula shown below it.

Good to know

Like every JoliTools calculator, it runs entirely in your browser with no account, no tracking, and no data leaving your device. Whether you're checking a discount, splitting a bill, or analyzing growth numbers, the math is instant and transparent.

Frequently asked questions

Divide X by 100 and multiply by Y. For example, 20% of 250 is (20 ÷ 100) × 250 = 50. The tool shows the formula with your numbers so you can follow along.

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