Three percentage questions, one tool. Pick what you want to find, type two numbers and get the answer instantly.
TL;DR X% of Y = X ÷ 100 × Y. X as a % of Y = X ÷ Y × 100. % change = (new − old) ÷ old × 100.
This free percentage calculator handles the three percentage questions students run into most: finding a percentage of a number, turning a score into a percentage, and working out a percentage increase or decrease. Everything runs in your browser, and the working is shown under every answer so you can copy the method into your homework.
How to use it
- Pick a mode: tap one of the three buttons above the boxes.
- Enter two numbers: the labels change to tell you exactly what goes where.
- Read the answer: the result updates as you type, with the formula and working underneath.
The three formulas
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | X ÷ 100 × Y | 15% of 80 = 0.15 × 80 = 12 |
| X is what % of Y? | X ÷ Y × 100 | 42 out of 50 = 0.84 × 100 = 84% |
| % change from X to Y | (Y − X) ÷ X × 100 | From 60 to 75 = 15 ÷ 60 × 100 = +25% |
Where students use percentages
- Test scores: 42 correct out of 50 is 84%. For a full grading chart, try the Test Score Calculator.
- Grade progress: went from 68% to 79% in a class? That is a 16.2% improvement, or 11 percentage points.
- Discounts and budgets: a 20% student discount on a $45 textbook saves you $9.
- Word limits: a 1,500-word essay with 10% leeway can run from 1,350 to 1,650 words. Check yours with the Word Counter.
Percent vs percentage points
If your grade moves from 70% to 77%, it rose by 7 percentage points but by 10 percent (because 7 is 10% of 70). Teachers, news articles and finance classes mix these up all the time, so it is worth knowing the difference.
FAQ
How do I calculate a percentage of a number in my head?
Find 10% by moving the decimal point one place left, then scale. For 15% of 80: 10% is 8, 5% is 4, so 15% is 12.
How do I turn a fraction or score into a percentage?
Divide the top number by the bottom number and multiply by 100. For 18/24: 18 ÷ 24 = 0.75, and 0.75 × 100 = 75%.
Why is a 50% drop not undone by a 50% rise?
Because the base changes. 100 falls 50% to 50, but a 50% rise on 50 only gets you to 75. To get back to 100 you need a 100% rise.
Can the percentage change be negative?
Yes. A negative result means a decrease. Going from 80 to 60 is a −25% change.