The three percentage formulas
A percentage is just a fraction out of 100. Every percentage question is one of these three, depending on which value you’re missing.
- A — the first number you enter
- B — the second number you enter
More detail
Percentage vs. percentage points
Going from 10% to 15% is a 5 percentage-point rise, but a 50% increase. News and finance often confuse the two — this calculator’s “percent change” mode gives the relative figure (50%), which is usually what’s meant by “X% more.”
Quick check. X% of Y always equals Y% of X. So 8% of 25 is the same as 25% of 8 = 2 — handy for doing percentages in your head.
Frequently asked questions
How do I calculate a percent increase?
Use the “percent change from A to B” mode: (B − A) ÷ A × 100. Going from 200 to 230 is (230−200)÷200×100 = 15% increase. Enter A=200, B=230 above to check.
How do I find what percent one number is of another?
Use “A is what % of B”: A ÷ B × 100. E.g. 15 is what % of 200 → 15÷200×100 = 7.5%. That's the same calculation as “15 out of 200.”
What is 15% of 200?
Use the “what is A% of B” mode: A ÷ 100 × B = 15 ÷ 100 × 200 = 30. Enter A=15, B=200 above to see it computed live.
What's the difference between percent change and percentage points?
Going from 10% to 15% is a 5 percentage-point rise, but a 50% increase relative to the starting value ((15−10)÷10×100). Use “percent change” mode when you want the relative figure, not the raw point difference.