Seven percentage calculations in one place, each with the working shown.
Quick answer
15% of 80 is 12. To find it, multiply 80 by 15 and divide by 100. A change from 80 to 100 is an increase of 25%.
| Percentage | Of 80 |
|---|---|
| 5% | 4.00 |
| 10% | 8.00 |
| 15% | 12.00 |
| 20% | 16.00 |
| 25% | 20.00 |
| 50% | 40.00 |
| 75% | 60.00 |
These figures are computed with the same formulas as the Percentage Calculator above. Change the inputs in the tool to see your own result.
The Percentage Calculator answers the seven questions people ask most, all on one page and all live: what is X% of Y, X is what percent of Y, the percentage change from one number to another, increase or decrease a number by a percentage, find the whole when you know a part and its percentage, and the percentage difference between two values. Each answer shows the working, so you can check homework, a discount or a price change and understand the result.
Made for everyone. Typical uses:
20% of 150 is 30. 30 is 25% of 120. A price that rises from 80 to 100 has gone up 25%, but a price that falls from 100 to 80 has dropped 20%, which is why percentage changes are not symmetric. Increasing 200 by 15% gives 230; decreasing it by 15% gives 170. If 40 is 25% of a number, that number is 160. The percentage difference between 50 and 70 is 33.33%.
Percentage change needs a non-zero starting value, because a change from zero has no percentage. Percentage difference divides by the average of the two numbers, which is different from percentage change; use the one that matches your question.
Accuracy: Formulas follow standard published methods and are checked against worked reference examples. Results are estimates based on the values you enter and do not replace advice from a qualified professional.
Expert Tip
To undo a percentage increase you cannot simply subtract the same percentage: if a price rises 25%, it must fall 20% to return to where it started.
Percentages are used everywhere: prices, grades, taxes, statistics, salaries and traffic reports. Most everyday problems fall into a few patterns, and the calculator has one box for each so you can find your question and see the answer with the working. The patterns are: what is X percent of Y; X is what percent of Y; percentage change from X to Y; increase Y by X percent; decrease Y by X percent; X is Y percent of what number; and the percentage difference between two values.
Each box updates as you type, shows the formula with your numbers and does not need a Calculate button, so you can compare scenarios quickly.
You can do most percentage maths by hand once you know three moves. To find a percentage of a number, divide the percentage by 100 and multiply: 20 percent of 150 is 0.20 × 150 = 30. To find what percentage one number is of another, divide the part by the whole and multiply by 100: 30 out of 120 is 25 percent. To find a percentage change, subtract the old from the new, divide by the old and multiply by 100: from 80 to 100 is a 25 percent increase.
The others follow from these. Increasing by X percent multiplies by (1 + X ÷ 100), and decreasing multiplies by (1 − X ÷ 100). Finding the whole from a part and its percentage divides the part by the percentage as a decimal: if 40 is 25 percent of a number, the number is 40 ÷ 0.25 = 160.
A 25 percent rise from 80 gives 100, but a fall from 100 back to 80 is only 20 percent. The percentage is always measured against the starting point, so the same absolute change is a different percentage depending on the direction. The same asymmetry applies to gains and losses on investments: a 50 percent loss needs a 100 percent gain to get back to where you started.
When you report a change, be explicit about the base. "Sales are up 25 percent from last year" and "last year's sales were 20 percent lower" describe the same facts but sound quite different. Percentage points are another common trap: a rate that goes from 4 percent to 5 percent has risen by one percentage point, but by 25 percent in relative terms.
Percentage change compares a new value with an old starting value. Percentage difference compares two values with no natural order, such as two products, two cities or two measurements, using their average as the base. The difference between 50 and 70 is 20 divided by the average of 60, or 33.33 percent, whichever value you enter first. Use change when there is a before and an after, and difference when you are comparing two things side by side.
Percentages appear in decisions that matter. A discount is a percentage off, and the Discount Calculator handles stacked offers and sales tax. Tax on a receipt is a percentage added, handled by the Sales Tax Calculator. A pay rise is a percentage change, and the Salary Calculator turns it into monthly and hourly amounts. Investment returns are percentages too: the ROI Calculator and the CAGR Calculator work with them.
For a tip, calculate the percentage of the pre-tax bill and add it. For grades, divide the marks obtained by the total marks and multiply by 100. For a business, profit margin is profit as a percentage of revenue, found with the Profit Margin Calculator.
A useful habit is to estimate before you calculate. Ten percent of any number is easy: move the decimal point one place. Five percent is half of that, and twenty percent is double. If the calculator says 20 percent of 150 is 30, ten percent (15) doubled agrees. The working line under each answer shows the formula with your numbers so you can verify the method as well as the result. Everything is calculated in your browser and nothing is sent or stored.
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