Percentage Calculator
A percentage calculator solves the three everyday percent questions: what X% of a number is, what percent one number is of another, and what the whole is when you know a part and its percent. Pick the question, type two numbers, and the answer appears with the formula and each step.
"Percent" means per hundred: 15% is 15 out of every 100
3 Percentage Formulas
Every percent problem has three numbers: a part, a whole and a percent. Know any two and one formula gives you the third.
Find the Part
"What is 15% of 200?"
Find the Percent
"30 is what percent of 200?"
Find the Whole
"30 is 15% of what number?"
How to Use the Percentage Calculator
Answer any percent question in 4 steps.
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Pick the Question
Choose What is X% of Y?, X is what % of Y? or X is Y% of what?
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Type the Two Numbers
Fill in the sentence. Decimals and negative numbers work too.
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Read the Result
The answer updates as you type. Press Enter or Calculate at any time.
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Check the Working
The formula and step-by-step box show exactly how the answer was found, so you can copy the method into homework.
Percentages on a 4 Function Calculator
You don't need a special calculator. Each formula is two or three key presses on any basic calculator.
15% of 200
30 Is What % of 200
30 Is 15% of What
Everyday Percentage Examples
Most real-life percent questions are one of the three formulas in disguise.
Sales Tax
8% tax on an $80 item. (More in the Sales Tax Calculator.)
Test Score
42 correct answers out of 50.
Savings Goal
$300 saved is 20% of the goal.
Battery Left
15% of a 4,000 mAh battery.
Common Percentages as Decimals & Fractions
To turn a percent into a decimal, divide by 100 (move the decimal point two places left). These are worth knowing by heart.
| Percent | Decimal | Fraction | Quick way to find it |
|---|---|---|---|
| 1% | 0.01 | 1/100 | Move the decimal point 2 places left |
| 5% | 0.05 | 1/20 | Half of 10% |
| 10% | 0.1 | 1/10 | Move the decimal point 1 place left |
| 12.5% | 0.125 | 1/8 | Divide by 8 |
| 20% | 0.2 | 1/5 | Divide by 5 |
| 25% | 0.25 | 1/4 | Divide by 4 |
| 33⅓% | 0.333… | 1/3 | Divide by 3 |
| 50% | 0.5 | 1/2 | Divide by 2 |
| 75% | 0.75 | 3/4 | Divide by 4, then × 3 |
| 100% | 1 | 1/1 | The whole number itself |
Want to do these by hand? Read the guide How to Calculate a Percentage, with mental-math shortcuts and practice problems.
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Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percent, then divide by 100. For example, 15% of 200 is 15 × 200 ÷ 100 = 30. You can also turn the percent into a decimal first: 200 × 0.15 = 30.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 42 out of 50 is 42 ÷ 50 × 100 = 84%.
How do I find the whole when I know a part and its percent?
Divide the part by the percent and multiply by 100. For example, if 300 is 20% of a number, the number is 300 ÷ 20 × 100 = 1,500.
Is X% of Y the same as Y% of X?
Yes. Both equal X × Y ÷ 100, so 8% of 50 and 50% of 8 are both 4. Swapping the numbers can turn a hard problem into an easy one: use the ⇄ Swap button to try it.
How do I calculate a percentage on a basic calculator?
Convert the percent to a decimal and multiply. For 15% of 200, press 200 × 0.15 =. Most basic calculators also accept 200 × 15 %, but the percent key works differently across brands, so the decimal method is the safest.
How do I convert a fraction to a percentage?
Divide the top number by the bottom number and multiply by 100. For example, 3/8 = 3 ÷ 8 = 0.375, and 0.375 × 100 = 37.5%.