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This percentage calculator handles six everyday sums, each with the formula and the steps behind the answer.
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A percentage is a number written as a fraction of 100, using the % sign. To find X% of Y, divide X by 100 and multiply by Y, so 15% of 200 is 0.15 × 200 = 30. To find what percent X is of Y, divide X by Y and multiply by 100.
The word comes from the Latin per centum, by a hundred. This percentage calculator covers the six questions people ask most, from a plain percent of a number to percent change and percent difference, and it shows each step so you can check the method or copy it into homework.
| Calculation | Formula | Example |
|---|---|---|
| X% of Y | X ÷ 100 × Y | 15% of 200 = 30 |
| X is what % of Y | X ÷ Y × 100 | 30 of 200 = 15% |
| X is Y% of what | X ÷ (Y ÷ 100) | 30 is 15% of 200 |
| Percent change | (new − old) ÷ |old| × 100 | 50 to 75 = +50% |
| Percent difference | |A − B| ÷ average × 100 | 10 and 15 = 40% |
| Increase or decrease | value × (1 ± % ÷ 100) | 500 + 10% = 550 |
Four steps. The answer updates while you type, so there is no Calculate button.
Choose one of the six calculations. The two boxes relabel themselves, so you always know which number goes where.
Type whole numbers or decimals. Commas such as 1,250 and a trailing % sign are fine, and the ± key makes a number negative on phone keypads that have no minus sign.
The answer comes with a plain sentence, related figures such as the reverse change, and the formula filled in with your numbers.
Copy the answer as a plain number for a spreadsheet, or copy a link that reopens the same calculation on any device.
Repeating decimals are cut at four places and marked with an ellipsis, and percentages are rounded to two decimals.
| Fraction | Decimal | Percentage |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/3 | 0.3333… | 33.33% |
| 2/3 | 0.6667… | 66.67% |
| 1/4 | 0.25 | 25% |
| 3/4 | 0.75 | 75% |
| 1/5 | 0.2 | 20% |
| 2/5 | 0.4 | 40% |
| 1/6 | 0.1667… | 16.67% |
| 1/8 | 0.125 | 12.5% |
| 3/8 | 0.375 | 37.5% |
| 1/10 | 0.1 | 10% |
| 1/20 | 0.05 | 5% |
| 1/100 | 0.01 | 1% |
| 3/2 | 1.5 | 150% |
| Number | 5% | 10% | 15% | 20% | 25% | 50% |
|---|---|---|---|---|---|---|
| 20 | 1 | 2 | 3 | 4 | 5 | 10 |
| 50 | 2.5 | 5 | 7.5 | 10 | 12.5 | 25 |
| 80 | 4 | 8 | 12 | 16 | 20 | 40 |
| 120 | 6 | 12 | 18 | 24 | 30 | 60 |
| 250 | 12.5 | 25 | 37.5 | 50 | 62.5 | 125 |
| 1,000 | 50 | 100 | 150 | 200 | 250 | 500 |
Three ways to compare 10 and 15 give three different answers. The right one depends on the question.
| Percent change | Percent difference | Percentage points | |
|---|---|---|---|
| Question it answers | How much did it grow or shrink from the start? | How far apart are two values, with neither as the base? | How far apart are two values that are already percentages? |
| Formula | (new − old) ÷ |old| × 100 | |A − B| ÷ ((|A| + |B|) ÷ 2) × 100 | new % − old % |
| 10 to 15 | +50% | 40% | +5 points (10% to 15%) |
| 15 to 10 | −33.33% | 40% | −5 points |
| Does order matter? | Yes | No | Yes |
| Typical use | Prices, sales, salaries and population over time | Two measurements, two quotes or two shops with no natural starting point | Interest rates, poll results, exam pass rates |
A 25% discount on 80 leaves 60. Use Increase or decrease by % with Decrease selected, and the facts line tells you how much you saved.
Add 18% to a bill of 64 to get 75.52, or add your local tax rate to a price. Pick 2 decimals to get a money-style answer.
42 correct out of 50 is 84%. Use X is what % of Y with the score first and the total second.
Rent that goes from 1,200 to 1,290 rose 7.5%. Percent change also shows what it would take to get back to the old figure.
Two scales read 10.2 kg and 10.6 kg. Percent difference compares them without treating either as the true value.
Find what share of your monthly spending goes on food, then track the categories with the expense calculator. For shares of hours worked, total them first with the online time calculator.
Most wrong answers come from the base of the percentage, not the arithmetic. To keep a list of results, paste them into the online notepad, and see the other free calculators on this site for dates, time and money.
100 plus 10% is 110, and 110 minus 10% is 99. The second change is taken from a bigger base.
A rate moving from 10% to 15% is up 5 percentage points, which is a 50% relative increase.
If a price is 60 after a 20% discount, the original was 60 ÷ 0.8 = 75, not 60 plus 20%. Use X is Y% of what with 60 and 80.
The formula divides by the starting value. When it is 0 the calculator shows the plain change instead.
The calculator divides by the size of the old value, so going from −10 to −5 reads as a +50% change. Some textbooks leave this case undefined.
Auto shows up to 2 decimals for percents and 4 for other numbers, while the maths keeps full precision. For a set number of significant figures, use the significant figures calculator.
It does not chain several changes or work out growth rates over many years. Apply successive changes one by one, using each answer as the next starting value.
Percent difference here uses the average of the two sizes as the base. Percent error in science uses the accepted value instead, as the relative change article explains.
Browsers store numbers with roughly 15 to 17 significant digits, so very long inputs are rounded. Answers of a quadrillion or more are shown in scientific notation.
The definitions on this page follow these references, last checked on November 9, 2026.
Short answers to the questions people ask most.
Divide the percent by 100 and multiply by the number. For example, 15% of 200 is 0.15 × 200 = 30.
Divide the part by the whole and multiply by 100. For example, 30 out of 200 is 30 ÷ 200 × 100 = 15%.
Subtract the old value from the new value, divide by the old value and multiply by 100. From 50 to 75 the change is 25 ÷ 50 × 100 = +50%, and a negative result means a decrease.
Percent change measures growth or shrinkage from a starting value, so the order matters. Percent difference compares two values against their average, so 10 and 15 give 40% in either order.
Divide the gap between the two values by their average and multiply by 100. For 10 and 15 that is 5 ÷ 12.5 × 100 = 40%.
Multiply the number by 1 plus or minus the percent written as a decimal. 500 increased by 10% is 500 × 1.1 = 550, and 500 decreased by 10% is 500 × 0.9 = 450.
Each change is measured from a different base. 100 rises to 110, and 10% of 110 is 11, so the decrease ends at 99.
Divide by the multiplier instead of multiplying. A price of 60 after a 20% discount was 60 ÷ 0.8 = 75, which the X is Y% of what mode gives when you enter 60 and 80.
A percentage point is the plain difference between two percentages. A rate that goes from 10% to 15% rises by 5 percentage points, which is a 50% relative increase.
Percent change divides by the starting value, and dividing by zero has no answer. The calculator shows the plain change instead.
Yes. Share link copies a web address that reopens the calculator with the same mode, numbers and decimal setting, and nothing is stored on a server.