How to use
- Pick the question you are asking from the tabs at the top.
- Type the two numbers. The result updates as you type.
- Read the plain-English sentence and the formula with your numbers filled in, then copy it or share the link.
Worked example: Three questions about the same numbers
What is 15% of 240? 15 ÷ 100 × 240 = 36. What percent of 240 is 36? 36 ÷ 240 × 100 = 15%.
If a price goes from 240 to 276, the percent change is (276 − 240) ÷ 240 × 100 = 15%. The percentage difference between 240 and 276, which does not care about direction, is 36 ÷ 258 × 100 = 13.95%.
Frequently asked questions
What is the difference between percent change and percentage difference?
Percent change has a direction: it divides by the old value. Percentage difference is symmetric: it divides by the average of the two values, so swapping them gives the same answer.
Why does percent change show "not defined" when the old value is 0?
Dividing by zero has no meaning. Going from 0 to anything is not a percentage increase, so the calculator says so instead of showing infinity.
How do I calculate a percent increase?
(end − start) ÷ |start| × 100. From 50 to 75 is a 50% increase. If the result is negative, it is actually a decrease and the calculator tells you.
How do I find the original number before a percent increase?
Divide by (1 + percent ÷ 100). If 120 is after a 20% increase, the original was 120 ÷ 1.2 = 100. The discount calculator has a reverse mode for prices.
Can I use negative numbers?
Yes. Percent change uses the absolute value of the old number so that going from −50 to 50 is a 200% increase.
Does it round?
Results are shown to 4 decimal places, rounded half up. The calculation itself is not rounded.