WorldCalcs

Percentage Calculator

What is X% of Y, X is what percent of Y, and percent change from A to B — three modes in one tool.

Reviewed by the WorldCalcs team · Methodology · Last reviewed: June 2026

Result

30

20% of 150 = 30

What is a percentage calculator?

A percentage calculator handles the three most common percentage questions: what is X% of a number, what percentage one number is of another, and the percentage change between two numbers. A percent simply means "per hundred".

How it works

For "X% of a number" it multiplies the number by X/100. For "A is what percent of B" it computes A ÷ B × 100. For percentage change it computes (new − old) ÷ old × 100. Examples: 20% of 150 is 30; 50 out of 200 is 25%; and 100 rising to 150 is a 50% increase.

All calculations happen in your browser. Nothing is sent, stored, or tracked.

Results are estimates and may contain errors — for general information only, not professional advice. Always verify before relying on them. Disclaimer

How to use

Pick a mode at the top of the card. Then fill in the two numbers — the result updates instantly as you type.

Percent of: (X ÷ 100) × Y. Is what percent: (X ÷ Y) × 100. Percent change: ((B − A) ÷ A) × 100. A negative result means a decrease.

Frequently asked questions

How is percent change calculated?+

Percent change from A to B = ((B − A) / A) × 100. If the result is negative, the value decreased; if positive, it increased.

Why is the result undefined when A is 0?+

You can't compute a percentage of zero — dividing by zero isn't defined. The same applies to 'X is what percent of Y' when Y is 0.

Does it support decimals and negative numbers?+

Yes. You can enter decimals (e.g. 12.5) and negative numbers. For percent change, a negative result means a decrease.

How do I find a percentage of a number?+

Multiply the number by the percent divided by 100. For 20% of 150: 150 × 0.20 = 30.

How do I work out what percent one number is of another?+

Divide the part by the whole and multiply by 100. 50 out of 200 = 50 ÷ 200 × 100 = 25%.

How do I calculate percentage change?+

Subtract the old value from the new, divide by the old value, and multiply by 100. From 100 to 150 = (150 − 100) ÷ 100 × 100 = 50%.

What is the difference between percentage and percentage points?+

A change from 10% to 15% is a rise of 5 percentage points, but a 50% increase relative to the starting value.

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