Percentage Calculator
Work out a percentage of a number, a ratio as a percent, or a percentage change.
- Calculation
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Three percentage calculations in one tool
Percentages describe a part out of one hundred. This calculator covers the three questions people ask most: what is X% of Y, X is what percent of Y, and the percentage change from A to B. Pick a mode, enter two numbers, and the answer updates as you type.
The formulas used
X% of Y is X ÷ 100 × Y. The share of X in Y is X ÷ Y × 100. The change from
A to B is (B − A) ÷ A × 100 — a positive result is an increase and a negative result is a
decrease. Every calculation happens in your browser.
How to use the Percentage Calculator
- Choose a mode. Select whether you want a percentage of a number, a ratio, or a change.
- Enter the first value. Type value X (or A for a change calculation).
- Enter the second value. Type value Y (or B for a change calculation).
- Read the result. See the answer and a plain-English explanation update instantly.
Frequently asked questions
How do I find what percent one number is of another?
Use the "X is what % of Y" mode. For example, 30 out of 120 is 30 ÷ 120 × 100 = 25%.
How is percentage change calculated?
Percentage change is (new − old) ÷ old × 100. Going from 200 to 250 is a 25% increase; going from 250 to 200 is a 20% decrease.
Why is a rise of 25% not cancelled by a fall of 25%?
Because each percentage is taken from a different base. A 25% rise from 200 gives 250, but a 25% fall from 250 gives 187.5, not 200.
Can I enter decimals or negative numbers?
Yes. Decimals work in every mode. Negative values are allowed for change calculations, though the base value cannot be zero.