To find P percent of a number, divide P by 100 and multiply: 20% of 50 = 0.20 × 50 = 10. This percentage calculator answers the three questions that every percent problem comes down to: what is P% of X, X is what percent of Y, and X is P% of what number. It shows the steps, the part and the remainder, and a chart of the part against the whole. Below it are quick answers to the most-searched questions, such as 20% of 60, 9 out of 12 as a percent and 15% of what number is 30, plus a grid of 5% to 95% of common numbers.
It is meant for students checking homework, shoppers working out a discount or a tip, and anyone reading a report that says something rose by a percentage. For changes between two values, such as a price going from $26 to $36, use the percentage increase calculator instead, because a change is measured against the starting value.
How to use the percentage calculator
- Choose the question. "What is P% of X?" finds a part. "X is what percent of Y?" finds a percent. "X is P% of what number?" finds the whole.
- Enter the two numbers you know. Decimals and percentages above 100 both work.
- Read the answer, then the steps. The part, the whole, the percent and the remaining share are all listed, so you can check each one.
- Copy the link to share a result. The question and the numbers are stored in the address, so the link opens on the same answer.
The percent formula
OpenStax Prealgebra defines a percent as a ratio whose denominator is 100, so 35% means 35 per 100, or 0.35. Every basic percent problem then fits one equation, which OpenStax builds by translating the words into symbols, reading "of" as multiplication and changing the percent to a decimal first. In its translations, "is" lands where the equals sign goes: "36 is 75% of what number?" becomes 36 = 0.75 · b.
part = percent × whole
- Find the part: part = (P ÷ 100) × whole. 35% of 90 = 0.35 × 90 = 31.5.
- Find the percent: percent = part ÷ whole × 100. 9 is what percent of 36? 9 ÷ 36 × 100 = 25%.
- Find the whole: whole = part ÷ (P ÷ 100). 31.5 is 35% of what? 31.5 ÷ 0.35 = 90.
These three examples are the same numbers OpenStax uses in its section on general applications of percent, so you can compare the calculator's steps with a textbook solution.
Mental shortcuts that are exact
- 10%: move the decimal point one place left. 10% of 75 is 7.5.
- 1%: move it two places. 1% of 75 is 0.75, so 3% is 2.25.
- Build from 10% and 5%: 15% = 10% + 5%. 15% of 75 = 7.5 + 3.75 = 11.25.
- Simple fractions: 50% is half, 25% is a quarter, 20% is a fifth, 75% is three quarters, 12.5% is an eighth.
- Swap the numbers: x% of y equals y% of x. 4% of 75 is hard; 75% of 4 is 3, the same answer.
Quick answers to common percent questions
Searches such as "20 of 75" or "30 of 40" can mean two different things: 20 percent of 75, or 20 out of 75 as a percentage. Where that happens, both answers are given.
What is 20 percent of 50?
20% of 50 is 10. Multiply 0.20 × 50 = 10. A quick check: 10% of 50 is 5, so 20% is twice that.
What is 20 percent of 60?
20% of 60 is 12: 0.20 × 60 = 12. 10% of 60 is 6, and doubling gives 12.
What is 10 of 100 (10% of 100)?
10% of 100 is 10, because percent means per hundred: 10 per 100 out of 100 is exactly 10. Read the other way, 10 is 10% of 100. Both answers are the same number only because the base is 100.
What is 20 of 75?
20% of 75 is 15 (0.20 × 75). If you mean "20 is what percent of 75", the answer is 20 ÷ 75 × 100 = 26.67%.
What is 20 as a percentage of 50?
20 is 40% of 50. Divide 20 ÷ 50 = 0.4, then multiply by 100 to get 40%.
What is 25 percent of 30?
25% of 30 is 7.5. 25% is one quarter, and 30 ÷ 4 = 7.5.
What is 80 percent of 15?
80% of 15 is 12: 0.80 × 15 = 12. Or take 10% of 15 (1.5) and multiply by 8.
What is 40 percent of 30?
40% of 30 is 12: 0.40 × 30 = 12. By the swap rule it equals 30% of 40, which is also 12.
What is 30 of 40?
30% of 40 is 12 (0.30 × 40). If you mean "30 out of 40 as a percent", it is 30 ÷ 40 × 100 = 75%, a common test-score question.
What is 15 of 75?
15% of 75 is 11.25 (0.15 × 75). And 15 is 20% of 75, because 15 ÷ 75 = 0.2.
15 percent of what number is 30?
30 is 15% of 200. Solve 30 = 0.15 × W, so W = 30 ÷ 0.15 = 200. Check: 15% of 200 is 30.
9 is what percent of 12?
9 is 75% of 12. 9 ÷ 12 = 0.75, and 0.75 × 100 = 75%.
What is 80 of 10 (80% of 10)?
80% of 10 is 8. Moving the decimal: 10% of 10 is 1, so 80% is 8. If you meant 80 as a percent of 10, that is 800%, more than the whole.
How do you find x percent of y?
Multiply x ÷ 100 by y. For x = 35 and y = 90 that is 0.35 × 90 = 31.5, the worked example used in OpenStax Prealgebra. Because x% of y = y% of x, pick whichever order is easier to do in your head.
"20 off 40" and other discount questions
A phrase like "20 off 40" nearly always comes from a price tag: it means 20 percent off a $40 item. That is a two-step question. OpenStax's discount rule is amount of discount = discount rate × original price, then sale price = original price − discount. The percent off and discount calculator does this with sales tax and stacked discounts.
What is 20 off 40?
20% off $40 is $32. The discount is 20% of 40 = $8, and $40 − $8 = $32. Equivalently, you pay 80% of the price: 0.8 × 40 = 32.
What is 30 off 100?
30% off $100 is $70. The discount is 30% of 100 = $30, and $100 − $30 = $70. Equivalently, you pay 70% of the price: 0.7 × 100 = 70.
What is 40 off 25?
40% off $25 is $15. The discount is 40% of 25 = $10, and $25 − $10 = $15. Equivalently, you pay 60% of the price: 0.6 × 25 = 15.
Percent of a number chart: 5% to 95%
Find the percent in the left column and the number along the top. Every cell is P% of the number, rounded to at most four decimals. Because x% of y = y% of x, the chart also answers questions like "50% of 8" by reading 8% of 50.
| Percent | of 10 | of 12 | of 15 | of 20 | of 25 | of 30 | of 40 | of 50 | of 60 | of 75 | of 80 | of 100 | of 120 | of 150 | of 200 | of 250 | of 500 | of 1,000 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 5% | 0.5 | 0.6 | 0.75 | 1 | 1.25 | 1.5 | 2 | 2.5 | 3 | 3.75 | 4 | 5 | 6 | 7.5 | 10 | 12.5 | 25 | 50 |
| 10% | 1 | 1.2 | 1.5 | 2 | 2.5 | 3 | 4 | 5 | 6 | 7.5 | 8 | 10 | 12 | 15 | 20 | 25 | 50 | 100 |
| 15% | 1.5 | 1.8 | 2.25 | 3 | 3.75 | 4.5 | 6 | 7.5 | 9 | 11.25 | 12 | 15 | 18 | 22.5 | 30 | 37.5 | 75 | 150 |
| 20% | 2 | 2.4 | 3 | 4 | 5 | 6 | 8 | 10 | 12 | 15 | 16 | 20 | 24 | 30 | 40 | 50 | 100 | 200 |
| 25% | 2.5 | 3 | 3.75 | 5 | 6.25 | 7.5 | 10 | 12.5 | 15 | 18.75 | 20 | 25 | 30 | 37.5 | 50 | 62.5 | 125 | 250 |
| 30% | 3 | 3.6 | 4.5 | 6 | 7.5 | 9 | 12 | 15 | 18 | 22.5 | 24 | 30 | 36 | 45 | 60 | 75 | 150 | 300 |
| 35% | 3.5 | 4.2 | 5.25 | 7 | 8.75 | 10.5 | 14 | 17.5 | 21 | 26.25 | 28 | 35 | 42 | 52.5 | 70 | 87.5 | 175 | 350 |
| 40% | 4 | 4.8 | 6 | 8 | 10 | 12 | 16 | 20 | 24 | 30 | 32 | 40 | 48 | 60 | 80 | 100 | 200 | 400 |
| 45% | 4.5 | 5.4 | 6.75 | 9 | 11.25 | 13.5 | 18 | 22.5 | 27 | 33.75 | 36 | 45 | 54 | 67.5 | 90 | 112.5 | 225 | 450 |
| 50% | 5 | 6 | 7.5 | 10 | 12.5 | 15 | 20 | 25 | 30 | 37.5 | 40 | 50 | 60 | 75 | 100 | 125 | 250 | 500 |
| 55% | 5.5 | 6.6 | 8.25 | 11 | 13.75 | 16.5 | 22 | 27.5 | 33 | 41.25 | 44 | 55 | 66 | 82.5 | 110 | 137.5 | 275 | 550 |
| 60% | 6 | 7.2 | 9 | 12 | 15 | 18 | 24 | 30 | 36 | 45 | 48 | 60 | 72 | 90 | 120 | 150 | 300 | 600 |
| 65% | 6.5 | 7.8 | 9.75 | 13 | 16.25 | 19.5 | 26 | 32.5 | 39 | 48.75 | 52 | 65 | 78 | 97.5 | 130 | 162.5 | 325 | 650 |
| 70% | 7 | 8.4 | 10.5 | 14 | 17.5 | 21 | 28 | 35 | 42 | 52.5 | 56 | 70 | 84 | 105 | 140 | 175 | 350 | 700 |
| 75% | 7.5 | 9 | 11.25 | 15 | 18.75 | 22.5 | 30 | 37.5 | 45 | 56.25 | 60 | 75 | 90 | 112.5 | 150 | 187.5 | 375 | 750 |
| 80% | 8 | 9.6 | 12 | 16 | 20 | 24 | 32 | 40 | 48 | 60 | 64 | 80 | 96 | 120 | 160 | 200 | 400 | 800 |
| 85% | 8.5 | 10.2 | 12.75 | 17 | 21.25 | 25.5 | 34 | 42.5 | 51 | 63.75 | 68 | 85 | 102 | 127.5 | 170 | 212.5 | 425 | 850 |
| 90% | 9 | 10.8 | 13.5 | 18 | 22.5 | 27 | 36 | 45 | 54 | 67.5 | 72 | 90 | 108 | 135 | 180 | 225 | 450 | 900 |
| 95% | 9.5 | 11.4 | 14.25 | 19 | 23.75 | 28.5 | 38 | 47.5 | 57 | 71.25 | 76 | 95 | 114 | 142.5 | 190 | 237.5 | 475 | 950 |
X out of Y as a percentage
Test scores and survey results are usually "what percent" questions: you have a part and a whole and need the percent. The table covers common totals.
| Score | Out of 10 | Out of 12 | Out of 20 | Out of 25 | Out of 40 | Out of 50 |
|---|---|---|---|---|---|---|
| 5 | 50% | 41.67% | 25% | 20% | 12.5% | 10% |
| 6 | 60% | 50% | 30% | 24% | 15% | 12% |
| 7 | 70% | 58.33% | 35% | 28% | 17.5% | 14% |
| 8 | 80% | 66.67% | 40% | 32% | 20% | 16% |
| 9 | 90% | 75% | 45% | 36% | 22.5% | 18% |
| 10 | 100% | 83.33% | 50% | 40% | 25% | 20% |
| 12 | — | 100% | 60% | 48% | 30% | 24% |
| 15 | — | — | 75% | 60% | 37.5% | 30% |
| 18 | — | — | 90% | 72% | 45% | 36% |
| 20 | — | — | 100% | 80% | 50% | 40% |
| 25 | — | — | — | 100% | 62.5% | 50% |
| 30 | — | — | — | — | 75% | 60% |
| 35 | — | — | — | — | 87.5% | 70% |
For a full course grade with weighted categories, the grade calculator combines several of these percentages.
Percent, percentage and percentage points
"Percent" is the unit (the % sign), and "percentage" is the number you get, though everyday English uses the two loosely. A percentage point is something else: the plain difference between two percentages. If a rate goes from 4% to 6%, it rose 2 percentage points, but it rose 50% relative to where it started. The U.S. Bureau of Labor Statistics makes the same distinction for price indexes: it reports moves as percent changes rather than index points, because index points depend on the starting level. The percentage increase calculator has a mode for percentage points.
Common mistakes
- Dividing the wrong way. "9 is what percent of 12" is 9 ÷ 12, not 12 ÷ 9. The whole (the number after "of") always goes on the bottom.
- Forgetting to divide by 100. 20% of 50 is 0.20 × 50, not 20 × 50.
- Treating a discount as the answer. 20% of $40 is the $8 you save; the price you pay is $32.
- Adding percentages of different bases. 10% of 50 plus 10% of 200 is not 20% of anything useful; work out each part first.
- Rounding too early. 20 ÷ 75 is 0.26666…, so 26.67% is rounded; multiply back with the unrounded value if you need the part again.
Related tools: work out a raise with the pay raise calculator, a restaurant tip with the tip calculator, and a sale price with the discount calculator.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percent by 100 and multiply by the number. 20% of 50 = 0.20 × 50 = 10. 12.5% of 80 = 0.125 × 80 = 10.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. 9 out of 12 is 9 ÷ 12 × 100 = 75%. 20 out of 50 is 40%.
How do I find the whole when I know the part and the percent?
Divide the part by the percent written as a decimal. If 30 is 15% of a number, the number is 30 ÷ 0.15 = 200.
What is 20% of 60?
12. 0.20 × 60 = 12.
What is 20% of 75?
15. One fifth of 75 is 15.
What is 25% of 30?
7.5. A quarter of 30 is 7.5.
What is 15% of 75?
11.25. 10% of 75 is 7.5 and 5% is 3.75; together they make 11.25.
Is x% of y the same as y% of x?
Yes. Both equal x × y ÷ 100. So 40% of 30 and 30% of 40 are both 12, and 8% of 25 is the same as 25% of 8, which is 2.
What does 20 off 40 mean?
In a shop it almost always means 20 percent off a $40 price: you pay $40 − $8 = $32. That is a discount question, which the percent off calculator handles with tax and stacked discounts.
Can a percentage be more than 100?
Yes. A part larger than the whole gives more than 100%. OpenStax's example: 144 is 150% of 96. 80 as a percent of 10 is 800%.
Sources & method
- OpenStax Prealgebra 2e, §6.1 Understand Percent — a percent is a ratio whose denominator is 100
- OpenStax Prealgebra 2e, §6.2 Solve General Applications of Percent — finding the amount, the base and the percent
- OpenStax Prealgebra 2e, §6.3 Solve Sales Tax, Commission, and Discount Applications — discount and sale price
- U.S. Bureau of Labor Statistics — CPI questions and answers: percent change versus index-point change
Results are estimates for general information. Found an error? It helps everyone — see our methodology.