Four of the most common percentage questions, answered as you type. Results update instantly and show the formula used, so you can check the working.
Percentage formulas
- X% of Y = Y × X ÷ 100. Example: 20% of 150 = 30.
- X is what % of Y = X ÷ Y × 100. Example: 30 is 25% of 120.
- % change = (new − old) ÷ old × 100. Example: 80 → 100 is a 25% increase.
Use these for discounts, tips, tax, grades, price rises and investment returns.
Questions
How do I calculate a discount?
Use “X plus/minus Y%”: the minus result is the sale price, e.g. 50 minus 10% = 45.
Why is a 50% drop followed by a 50% rise not back to the start?
The rise is calculated on the smaller number: 100 → 50 → 75.
How do I work out percentage points?
Percentage points are a plain subtraction of two percentages: 40% to 45% is +5 points, but a 12.5% increase.