Percentage Calculator
The three percentage questions everyone actually asks — each solved instantly as you type.
1. What is X% of Y?
2. X is what percent of Y?
3. Percentage change from X to Y
The three formulas
| Question | Formula | Example |
|---|---|---|
| What is 15% of 200? | 200 × 15 ÷ 100 | 30 |
| 45 is what % of 180? | 45 ÷ 180 × 100 | 25% |
| Change from 80 to 100? | (100 − 80) ÷ 80 × 100 | +25% |
The classic mistake: percentage change direction
A 25% increase followed by a 25% decrease does not return you to the start: 80 → 100 → 75. Percentage change is always relative to the starting value, so the same absolute change is a bigger percentage of a smaller number. This is why a stock that drops 50% needs a 100% gain to recover.
Percentage points vs. percent
If a tax rate rises from 10% to 12%, it rose 2 percentage points but 20 percent (2 ÷ 10). News headlines mix these up constantly; now you won't.
Frequently asked questions
How do I calculate a percentage discount?
Multiply the price by (100 − discount) ÷ 100. A $60 item at 30% off: 60 × 0.7 = $42. Our discount calculator handles stacked discounts and sales tax too.
How do I reverse a percentage (find the original price)?
Divide by the multiplier instead of multiplying. If $42 was the price after 30% off, the original was 42 ÷ 0.7 = $60. If $113 includes 13% tax, the pre-tax price is 113 ÷ 1.13 = $100.
How do I add percentages together?
Sequential percentages multiply, not add: two successive 10% increases give 1.1 × 1.1 = 1.21, a 21% total increase — not 20%.