Percentage calculator
Four quick percentage tools on one page: what is X% of Y, X is what percent of Y, the percentage change from one value to another, and a value increased or decreased by a percentage. Every answer appears as you type, with the formula spelled out so you can check it — handy for discounts, price changes, returns, tips and sales tax.
What is X% of Y?
Result
30
150 × 20 ÷ 100 = 30
Multiply the number by the percentage and divide by 100.
X is what percent of Y?
Result
25%
30 ÷ 120 × 100 = 25%
Divide the part by the whole and multiply by 100.
Percentage change from A to B
Result
+25%increase
(100 − 80) ÷ |80| × 100 = +25%
Divide the difference by the starting value and multiply by 100.
Increase or decrease by a percentage
Result
230
200 × (1 + 15 ÷ 100) = 230
Multiply by 1 + X/100 to increase, or by 1 − X/100 to decrease.
Percentage formulas with examples
X% of Y
Y × X ÷ 100
20% of 150 = 150 × 20 ÷ 100 = 30
X as a percentage of Y
X ÷ Y × 100
30 out of 120 = 30 ÷ 120 × 100 = 25%
Percentage change from A to B
(B − A) ÷ |A| × 100
From 80 to 100: (100 − 80) ÷ 80 × 100 = +25%. Going back from 100 to 80 is −20%.
Increase or decrease by X%
A × (1 + X ÷ 100) or A × (1 − X ÷ 100)
200 + 15% = 200 × 1.15 = 230; 200 − 15% = 200 × 0.85 = 170
Common percentage mistakes
- Falling and rising by the same percentage does not bring you back: 100 − 50% = 50, and 50 + 50% = 75. After a fall you need a bigger rise to recover — see the loss-recovery table in the profit/loss calculator.
- Percent vs. percentage points: an interest rate going from 10% to 12% rose by 2 percentage points, which is a 20% increase.
- Taking off a percentage that was added: to get the price before a 20% tax, divide by 1.20 rather than subtracting 20%. 120 ÷ 1.20 = 100, while 120 − 20% = 96.
- Changes don't add up: +10% followed by another +10% is +21% in total, not +20%.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 is 150 × 20 ÷ 100 = 30.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 out of 120 is 30 ÷ 120 × 100 = 25%.
How do I calculate percentage change?
Subtract the old value from the new one, divide by the old value and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = +25%.
How do I add or subtract a percentage?
To increase a number by X%, multiply it by (1 + X/100); to decrease it, multiply by (1 − X/100). 200 increased by 15% is 230, and decreased by 15% it is 170.
How do I find the price before a percentage was added?
Divide by (1 + X/100). A price of 120 that includes 20% tax was 120 ÷ 1.20 = 100 before tax.