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Percentage Calculator
Choose a calculation, enter two numbers, and see the result instantly — with the formula and each step shown. All calculations happen in your browser.
Find a percentage of a number, for example a discount amount or a tax amount.
What a percentage means
A percentage is a number out of 100. The word comes from “per cent”, meaning per hundred, so 25% means 25 out of every 100, and 100% means the whole amount. Percentages let you compare amounts of different sizes: 45 out of 60 and 90 out of 120 are both 75%. To turn a percentage into a decimal, divide by 100, so 25% becomes 0.25; to turn a decimal into a percentage, multiply by 100.
Percentage of a number
To calculate a percentage of a number, divide the percentage by 100 and multiply by the number. This is the calculation behind discounts, tips, and tax. If a jacket costs 150 and is reduced by 20%, the reduction is 20 ÷ 100 × 150 = 30, so the sale price is 120. The same method finds a share of a total: 12.5% of 200 is 25. Percentages over 100% are also possible: 150% of 80 is 120.
Percentage increase and decrease
Percentage change measures how much a value has moved compared with where it started. For an increase, subtract the original value from the new value, divide by the original value, and multiply by 100. A salary rising from 80 to 100 has increased by (100 − 80) ÷ 80 × 100 = 25%. For a decrease, subtract the new value from the original value and use the same base: a price falling from 200 to 150 has decreased by (200 − 150) ÷ 200 × 100 = 25%. Notice that the base matters: going from 80 to 100 is a 25% increase, but returning from 100 to 80 is only a 20% decrease, because the second calculation starts from the larger number.
Percentage difference
Percentage difference is a different idea. It compares two values without treating either one as the starting point, so the answer is the same whichever order you enter them in. Instead of dividing by one value, you divide the absolute difference by the average of the two values. The percentage difference between 80 and 100 is therefore |100 − 80| ÷ 90 × 100, about 22.22%. Use it when neither value is clearly “before” and the other “after”, for example when comparing two prices. Use increase or decrease when there is a clear original value and a later value.
Formulas at a glance
| Calculation | Formula |
|---|---|
| What is X% of Y? | X ÷ 100 × Y |
| X is what percent of Y? | X ÷ Y × 100 |
| Percentage increase | (Y − X) ÷ X × 100 |
| Percentage decrease | (X − Y) ÷ X × 100 |
| Percentage difference | |X − Y| ÷ ((X + Y) ÷ 2) × 100 |
Worked examples
- 20% of 150 is 30. Convert 20% to 0.20, then multiply: 0.20 × 150 = 30. A 20% discount on a 150 item therefore saves 30, leaving a price of 120.
- 45 is 25% of 180. Divide the part by the whole and multiply by 100: 45 ÷ 180 × 100 = 25%. A test score of 45 out of 180 is a 25% score.
- From 80 to 100 is a 25% increase, but the percentage difference is 22.22%. The increase uses the original value as its base: (100 − 80) ÷ 80 × 100 = 25%. The difference uses the average, 90, as its base: 20 ÷ 90 × 100 = 22.22%.
Common mistakes to avoid
Do not confuse percentage points with percent. Moving from 20% to 25% is a rise of 5 percentage points, but a 25% relative increase, because 5 ÷ 20 × 100 = 25%. A second mistake is using the wrong base, especially after a price has already changed. A third is dividing by zero: a percentage of a zero whole, or a change from a zero original value, has no meaningful answer, so this calculator explains that instead of showing a number. Finally, this calculator rounds to two decimal places, so keep more precision if you feed a result into another calculation.
Note: For general information only. Results are rounded to two decimal places.
Related tools
- Percentage Increase Calculator
Find a percentage increase, with original, new, and absolute change shown.
- Percentage Decrease Calculator
Find a percentage decrease, with original, new, and absolute change shown.
- About
What this site is and how it works.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100, then multiply by the number. For example, 20% of 150 is 20 ÷ 100 × 150 = 30. If a shop price is 150 and the discount is 20%, the discount amount is 30 and the price after the discount is 120.
What is the difference between percentage increase and percentage difference?
Percentage increase compares a new value with an original value, using the original value as the base, so it depends on direction: going from 80 to 100 is a 25% increase, but going from 100 to 80 is a 20% decrease. Percentage difference instead uses the average of the two values as the base, so it is the same in both directions: the percentage difference between 80 and 100 is about 22.22%.
How do I calculate percentage increase?
Subtract the original value from the new value, divide by the original value, and multiply by 100. For example, a salary rising from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%. The original value must not be zero, because a percentage increase from zero is undefined.
How do I calculate percentage decrease?
Subtract the new value from the original value, divide by the original value, and multiply by 100. For example, a price falling from 200 to 150 is (200 − 150) ÷ 200 × 100 = 25%. If the new value is higher than the original, the result is negative, which means the value actually rose.
Can a percentage be more than 100%?
Yes. A percentage over 100% simply means the part is larger than the whole you compared it with. For example, 180 is 150% of 120, because 180 ÷ 120 × 100 = 150%. A percentage increase can also exceed 100%: a value doubling from 50 to 100 is a 100% increase, and tripling from 50 to 150 is a 200% increase.
Do you store the numbers I enter?
No. All calculations happen in your browser. Nothing is sent to a server, stored in a database, or tied to an account, because this site has no backend at all.