Percentage Calculator
Six percentage calculators in one: X% of Y, what percent, percentage change, increase or decrease, discount price and reverse percentage.
About the Percentage Calculator
Every everyday percentage question in one place: work out a tip or tax, the percentage change between two prices, a sale price after discount, or the original price before a percentage was added. Results update as you type.
How to use it
- Pick the calculator that matches your question.
- Type the two numbers.
- Read the answer, along with the formula used.
The formulas, in plain words
X% of Y is Y × X ÷ 100: 15% of 200 is 30. X as a percentage of Y is X ÷ Y × 100: 30 out of 120 is 25%. Percentage change is (new − old) ÷ old × 100: going from 80 to 100 is a 25% increase. Increasing Y by X% is Y × (1 + X ÷ 100), and decreasing it is Y × (1 − X ÷ 100).
Discounts and prices that already include tax
A 25% discount on 4,999 saves 1,249.75, so you pay 3,749.25. To find a price before a percentage was added, divide rather than subtract: if 1,150 includes 15% tax, the original price is 1,150 ÷ 1.15 = 1,000 and the tax was 150. Subtracting 15% of 1,150 would give the wrong answer.
Common mistakes
Percentages don't cancel out: a 20% rise followed by a 20% fall leaves you 4% below where you started. Percentage points are not percentages either — an interest rate moving from 10% to 12% is a 2 percentage point rise but a 20% increase in the rate.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 200 is 200 × 15 ÷ 100 = 30.
How do I calculate percentage change?
Subtract the old value from the new value, divide by the old value and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25% increase.
Why isn't a 20% increase undone by a 20% decrease?
Because the second percentage applies to a different base. 100 + 20% = 120, but 120 − 20% = 96. To reverse a 20% increase you need a 16.67% decrease.