How to calculate percentages
- Find the question that matches yours, such as "What is X% of Y?" or "Percentage change from X to Y".
- Type your two numbers into the boxes. Decimals, negative numbers, and commas as thousands separators all work.
- Read the answer, the sentence, and the formula with your numbers filled in below the boxes.
Each form works on its own, so you can use several at once. For example, check a discount and then work out what the full price was.
Percentage formulas
| Question | Formula | Example |
|---|---|---|
| X% of Y | X ÷ 100 × Y | 15% of 200 = 30 |
| X is what % of Y | X ÷ Y × 100 | 30 is 15% of 200 |
| % change from X to Y | (Y − X) ÷ |X| × 100 | 80 to 100 = +25% |
| Add X% to Y | Y × (1 + X ÷ 100) | 50 + 20% = 60 |
| Subtract X% from Y | Y × (1 − X ÷ 100) | 50 − 20% = 40 |
| Y is X% more than what | Y ÷ (1 + X ÷ 100) | 150 is 25% more than 120 |
| Y is X% less than what | Y ÷ (1 − X ÷ 100) | 75 is 25% less than 100 |
Questions
Are my numbers stored or sent anywhere?
No. Every answer is worked out in your browser while you type. Nothing is uploaded, saved, or tracked.
How do I calculate a percentage increase or decrease?
Subtract the old value from the new one, divide by the old value, and multiply by 100. Use the "Percentage change from X to Y" form: a price going from 80 to 100 is a 25% increase, and going from 100 back to 80 is a 20% decrease. The two are different because each percentage is measured against its own starting value.
How do I add a percentage, like tax or a tip, to a price?
Use "Add or subtract a percentage". Adding 20% to 50 gives 60, found by multiplying 50 by 1.20. Choose "Subtract" for a discount: 20% off 50 is 40.
What does the reverse percentage form do?
It finds the original number before a percentage was added or taken off. If a price including 25% extra is 150, the original was 120. This is how you take VAT or sales tax out of a total, or work out a price before a sale.
Why is my percentage change different when I swap the numbers?
Because the starting value changes. Going from 50 to 75 is up 50%, but going from 75 to 50 is down about 33.3%. Percentage points, such as a rate rising from 4% to 6%, are a different thing again: that is 2 percentage points, or a 50% relative increase.
Credits
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