Percentage Calculator
Quickly work out percentages — a share of a number, a ratio as a percent, or a percentage change between two values.
How to use
- Type the percentage and the number to find a share of it.
- Use the second box to express one number as a percent of another.
- Use the third box for percentage increase or decrease between two values.
How the Percentage Calculator works
Handles the three percentage questions people actually ask: what is X% of Y, X is what percent of Y, and what is the percentage change from X to Y.
Each is a different rearrangement of the same relationship between a part, a whole and a rate.
X% of Y = Y × X/100
part ÷ whole × 100 = percent
(new − old) ÷ old × 100 = % change
Worked example
20% of 250 is 50. 45 out of 60 is 75%. Going from 80 to 100 is a 25% increase; going back from 100 to 80 is a 20% decrease.
Things worth knowing
- A percentage increase and the decrease that reverses it are never equal, because the base changes. Up 50% then down 50% leaves you at 75% of where you started.
- Percentage points and percent are different. Moving from 10% to 12% is a rise of 2 percentage points but 20 percent.
- For successive changes, multiply the factors: +10% then +10% is ×1.1×1.1 = ×1.21, not +20%.
Frequently asked questions
How do I calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 of 200 is 30 ÷ 200 × 100 = 15%.
How do I work out a percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100.
How do I calculate a percentage decrease?
Subtract the new value from the old, divide by the old, and multiply by 100. Always divide by the original figure.
Why does a 50% loss need a 100% gain to recover?
Because the gain is measured against the smaller remaining amount. 100 falls to 50, and 50 must double to return to 100.