Percentage Calculator
Work out percentages, percentage change and reverse percentages.
Percentage
= 15% × 240 ÷ 100
Private by design. Everything runs locally in your browser. Your input is never uploaded, logged or stored on a server.
How to use the Percentage Calculator
- Pick the calculation: X% of Y, X is what % of Y, percentage change, or reverse percentage.
- Fill in the two values you know.
- Read the result together with the remainder — the other part of the whole.
- For a change, read the asymmetry note before assuming the reverse move is the same figure.
A worked example
change from 80 to 100
+25% · going back from 100 to 80 is −20%
Percentage change is not symmetric, and this is where most percentage mistakes live. A 25% rise and a 20% fall cancel out exactly.
Frequently asked questions
How do I calculate percentage change?
Subtract the old value from the new value, divide by the old value, then multiply by 100. From 80 to 100 is (100 − 80) / 80 × 100 = 25%.
Why is a 50% rise not cancelled by a 50% fall?
Because each percentage applies to a different base. 100 rising 50% gives 150; 150 falling 50% gives 75. To return to 100 from 150 you need a 33.3% fall.
How do I remove a percentage that has already been added?
Divide rather than subtract. To strip 20% tax from a gross price of 120, calculate 120 / 1.20 = 100.
What is the difference between percent and percentage points?
A move from 5% to 7% is a rise of 2 percentage points, but a 40% increase. Financial reporting uses the distinction precisely.
About the Percentage Calculator
Four separate questions get bundled under "percentage", and mixing them up is the usual source of error. Each has its own tab here, with the formula shown alongside the result.
X% of Y scales a number: 15% of 240 is 36. X is what % of Y expresses a part as a share of a whole. Percentage change measures movement from an old value to a new one, and is asymmetric — a rise from 100 to 150 is +50%, but the fall back from 150 to 100 is −33.3%, not −50%. Reverse percentage recovers the original before an increase or discount was applied, which is how you strip VAT from a gross figure.
The reverse case is the one most often done wrong: taking 20% off a price that already includes 20% tax does not return the pre-tax price. Divide by 1.2 instead of multiplying by 0.8.
Maintained by Ikonode. Last checked against the code on 11 September 2026.
What it does not do
- Arithmetic only. It has no opinion about whether the percentage is the right one to use.
- Percentage points and percent are different things: 5% to 7% is a rise of two percentage points, or of 40%.
- Rounding is applied for display; the underlying calculation keeps full precision.