At a glance
| Three questions | What is X% of Y; X is what percent of Y; the change from X to Y |
|---|---|
| Output | The answer and the arithmetic behind it |
| Where it runs | Entirely in your browser — no file is uploaded to a server |
| Price | Free, with no account and no sign-up |
| Offline | Works with no connection after the first visit |
Percent change and percentage points are different
If a rate goes from 4% to 6%, that is a rise of two percentage points and a 50% increase. Both are true and they describe the same change very differently — which is why the choice between them is a favourite of anyone presenting a number in its best light.
Worth knowing in both directions: when a headline reports a "50% rise" in something already measured as a percentage, find out which one it means.
An increase and a decrease do not cancel
Up 50% then down 50% does not return to where you started. 100 becomes 150 and then 75, because the second percentage applies to a larger base. To reverse a 50% rise you need a 33.3% fall.
The same asymmetry is why an investment that loses 50% needs to gain 100% to break even.
Frequently asked questions
What is the difference between a percentage point and a percent?
A move from 4% to 6% is two percentage points and a 50% increase. Both are correct and they sound very different, which is why the choice is often deliberate.
Why does up 50% then down 50% not return to the start?
The second percentage applies to a bigger number. 100 goes to 150 then to 75. To undo a 50% rise you need a 33.3% fall.
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100. The tool does it in every direction, including finding the original from a result.
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