Percentage Calculator
Four quick percentage calculators in one place. The answers update as you type.
1. What is X% of Y?
2. X is what percent of Y?
3. Percentage change from one number to another
4. Increase or decrease a number by a percentage
The four percentage formulas
X% of Y is X divided by 100, multiplied by Y. So 15% of 200 is 0.15 x 200 = 30.
X is what percent of Y is X divided by Y, multiplied by 100. So 30 out of 120 is 30 / 120 x 100 = 25%.
Percentage change is the new value minus the old value, divided by the old value, multiplied by 100. Going from 80 to 100 is (100 - 80) / 80 x 100 = +25%. A negative answer means the value went down.
Increasing or decreasing by a percentage means multiplying by (1 + X/100) or (1 - X/100). Adding 10% to 200 gives 200 x 1.10 = 220, and taking 10% off gives 200 x 0.90 = 180.
These calculations help with sale prices, marks and scores, tips, growth figures and many everyday questions. Everything runs in your browser.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 20% of 350 is 0.20 x 350 = 70.
How do I work out percentage increase or decrease?
Subtract the old value from the new value, divide by the old value and multiply by 100. A positive result is an increase and a negative result is a decrease.
How do I find the original number before a percentage increase?
Divide the new number by (1 + the percentage as a decimal). If a price is 120 after a 20% increase, the original was 120 / 1.20 = 100.
Why does a 10% increase followed by a 10% decrease not return to the start?
The decrease is taken from the larger number. Starting at 100, adding 10% gives 110, and taking 10% off 110 gives 99, not 100.
What is the difference between percent and percentage points?
Going from 4% to 5% is a rise of 1 percentage point, but it is a 25% increase in the rate itself, because 1 is a quarter of 4.