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Percentage Calculator
Work out any percentage in seconds: what percent of a number, what percentage one number is of another, percentage increase or decrease, and how to increase or decrease a number by a percent. Type a number or drag a slider and the answer updates live — no sign-up, nothing saved.
Current as of November 2026. All calculations run entirely in your browser.
What is X% of Y?
Find a percentage of any number — for example, a 20% discount on a $250 item.
20% of 250 = 50 · 250 − 50 = 200 left after taking 20% off.
What percentage is X of Y?
Find what share one number is of another — for example, 50 out of 250 is what percent?
50 is 20% of 250 · 50 ÷ 250 × 100 = 20%.
Percentage increase / decrease
How much did a value change in percent — for example, a price rising from $100 to $125?
Increase of 25% · (125 − 100) ÷ 100 × 100 = +25% · Change: +25.
Increase / decrease a number by a percentage
Add or subtract a percent from a number — for example, a 15% pay rise on $200, or 15% off $200.
200 increased by 15% = 230 · 200 × 1.15 = 230 · Change: +30.
Worked examples
Four quick examples you can check by hand — and try in the calculator above.
What is 20% of 250?
50
250 × 20 ÷ 100 = 50. So a 20% tip on $250 is $50.
50 is what percent of 250?
20%
50 ÷ 250 × 100 = 20%. So 50 out of 250 is one fifth.
Increase from 100 to 125
+25%
(125 − 100) ÷ 100 × 100 = +25%. The value grew by a quarter.
200 increased by 15%
230
200 × 1.15 = 230. The increase itself is 200 × 15% = 30.
How it works
A percentage is simply a number out of 100. The word comes from the Latin per centum — “by the hundred.” Every calculation below follows from that one idea, and the calculator above applies the formula the moment you change a value.
1. What is X% of Y?
Multiply the number by the percentage, then divide by 100. 20% of 250 is 250 × 20 ÷ 100 = 50. Use this for discounts, tips, tax, commission and interest.
2. What percentage is X of Y?
Divide the part by the whole and multiply by 100. 50 ÷ 250 × 100 = 20%. Use this for test scores, completion rates, market share and vote shares.
3. Percentage increase or decrease
Subtract the old value from the new value, divide by the old value and multiply by 100. A positive answer is an increase, a negative answer is a decrease. From 100 to 125 is (125 − 100) ÷ 100 × 100 = +25%.
4. Increase or decrease a number by a percentage
To increase 200 by 15%, multiply by 1.15 to get 230. To decrease 200 by 15%, multiply by 0.85 to get 170. Use this for pay rises, price rises, sales and mark-downs.
Frequently asked questions
How do I calculate what percentage of a number is?
Multiply the number by the percentage and divide by 100. For example, 20% of 250 is 250 × 20 ÷ 100 = 50. Enter the percentage and the number in the first tab above and the answer appears instantly.
How do I work out what percentage one number is of another?
Divide the first number by the second number and multiply by 100. For example, 50 is 50 ÷ 250 × 100 = 20% of 250. This is the same formula used for test scores: 18 correct out of 20 questions is 18 ÷ 20 × 100 = 90%.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value, and multiply by 100. Going from 100 to 125 is (125 − 100) ÷ 100 × 100 = +25%. If the new value is smaller, the same formula gives a negative number — a percentage decrease.
How do I increase a number by a percentage?
Multiply the number by 1 plus the percentage as a decimal. Increasing 200 by 15% is 200 × 1.15 = 230. To decrease it, multiply by 1 minus the percentage: 200 × 0.85 = 170. Use the fourth tab above and switch between Increase and Decrease.
What is the difference between percentage points and percent?
Percentage points measure the simple difference between two percentages, while percent measures the relative change. Going from 20% to 25% is a rise of 5 percentage points, but a 25% increase relative to the original 20% — because 5 ÷ 20 × 100 = 25%.
Is this percentage calculator free to use?
Yes. The ToolNly Percentage Calculator is completely free, needs no sign-up, and runs entirely in your browser — nothing you type is saved or sent anywhere.
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