What Percent Calculator
The what percent calculator answers the question "X is what percent of Y?" Enter a part (the value you want to find the percentage of) and a whole (the reference value), and the calculator returns the percentage. For example, 20 is what percent of 100? The answer is 20%. This is one of the most frequently used percentage calculations, useful for scoring, market analysis, composition analysis, and countless other contexts. The formula is simple: percentage = (part / whole) * 100. The calculator also works in reverse: given a percentage and a whole, find the part. For example, if you want to find what number is 20% of 100, the calculator will return 20.
What percent formula
Percentage = (part / whole) * 100
Common examples
| Part | Whole | Percentage | Context |
|---|---|---|---|
| 20 | 100 | 20% | 20 out of 100 items |
| 15 | 50 | 30% | Test score (15 out of 50) |
| 3 | 4 | 75% | Completion (3 of 4 tasks) |
| 1 | 8 | 12.50% | Portion of a whole |
| 150 | 100 | 150% | Exceeding target (150% of goal) |
What percent calculator: frequently asked questions
What does 'what percent' mean?
When you ask 'What percent of 100 is 20?', you are finding what percentage one number is of another. The answer is 20%, because 20 is 20% of 100. This is one of the most common percentage questions in real life.
How do I calculate 'what percent'?
The formula is: percentage = (part / whole) * 100. For example, to find what percent of 80 is 20, calculate (20 / 80) * 100 = 25%. Alternatively, divide the part by the whole to get a decimal (20 / 80 = 0.25), then multiply by 100 to convert to a percentage.
What is the difference between 'what percent' and 'percent of a number'?
'What percent' answers 'What percent of 100 is 20?' (answer: 20%). 'Percent of a number' answers 'What is 20% of 100?' (answer: 20). They are reciprocal questions.
Can the percentage be more than 100%?
Yes. If the part is larger than the whole, the percentage will exceed 100%. For example, what percent of 50 is 75? The answer is 150%. This can happen when comparing a value to a smaller baseline.
When would I use this calculation?
Common uses include calculating test scores (20 out of 50 questions is what percent?), market share (50 million out of 500 million customers is what percent?), and composition (how much of a mixture is one ingredient as a percentage?).
Official sources
- Standard mathematical formula for what percent.
- NIST Special Publication 330: The International System of Units.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.