Percentage Calculator
Find X% of Y, work out what percent one number is of another, or calculate a percentage increase or decrease. Pick a calculation below and get an instant, exact result.
How to use the Percentage Calculator
Pick the tab that matches your question. "X% of Y" tells you what a percentage of a number equals — useful for tips, discounts, and commissions. "X is what % of Y" tells you what percentage one number represents of another — useful for test scores, quotas, and market share. "% Increase / Decrease" tells you how much a value has grown or shrunk between two points — useful for price changes, salary raises, and growth rates.
Enter your numbers and click Calculate to see the exact result along with the formula used, so you can see exactly how the answer was reached.
Percentage formulas explained
1. X% of Y — used to find a percentage of a number, such as calculating a tip, a discount, or a commission.
2. X is what % of Y — used to express one number as a percentage of another, such as a test score out of a total or a portion of a budget.
3. Percentage change — used to measure growth or decline between an old value and a new value, such as a price change or a year-over-year comparison.
All three calculations use only basic arithmetic, so results are exact — there's no rounding or approximation beyond standard decimal display.
Frequently Asked Questions
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How do I calculate X% of Y?
Divide X by 100, then multiply by Y: (X ÷ 100) × Y. For example, 20% of 150 is (20 ÷ 100) × 150 = 30.
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How do I find out what percent one number is of another?
Divide the first number by the second, then multiply by 100: (X ÷ Y) × 100. For example, 30 is what percent of 150? (30 ÷ 150) × 100 = 20%.
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How do you calculate percentage change or percentage increase/decrease?
Subtract the old value from the new value, divide by the absolute value of the old value, then multiply by 100: ((New − Old) ÷ |Old|) × 100. A positive result is a percentage increase; a negative result is a percentage decrease.
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Why use the absolute value of the old number in percentage change?
Using the absolute value of the old (starting) number keeps the sign of the result meaningful — a change from a negative starting value still shows correctly as an increase or decrease rather than flipping sign unexpectedly.
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What's the difference between percentage points and percent change?
A percentage point is a simple difference between two percentages — going from 40% to 50% is a 10 percentage point increase. Percent change measures that same move relative to the starting value: (50 − 40) ÷ 40 × 100 = 25% change.
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Is my data kept private?
Yes — all calculations run entirely in your browser using JavaScript. Nothing you enter is transmitted to any server or stored anywhere. See our Privacy Policy for full details.