Percentage Change Calculator Calculators
Measure growth or decline between two numbers.
Percentage Change Calculator is a free online tool that measure growth or decline between two numbers. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free: no account, no quota, no watermark
- Category
- Calculators
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 2
- Works offline
- Yes, after the first visit
About Percentage Change Calculator
Percentage change is always measured against the starting value, and that asymmetry catches people out constantly. A number that rises 20% and then falls 20% does not return to where it began: 100 becomes 120, and 20% off 120 is 96. To undo a 20% rise you need a fall of 16.67%. The same trap runs the other way, which is why a stock that halves needs to double just to break even. Change from a starting value of zero has no defined percentage at all, since there is nothing to divide by, and this reports that rather than showing infinity.
How to use it
- Enter starting value and ending value.
- Results update the moment anything changes.
The 2 settings
| Setting | What it does | Default |
|---|---|---|
| Starting value | A numeric value. | 120 |
| Ending value | A numeric value. | 150 |
Under the hood
| Runs on | plain JavaScript: runs the whole thing |
| Controls | Starting value, Ending value |
Questions
Is the arithmetic exact?
It uses double-precision floating point: about 15 significant figures, far more than the inputs justify. Displayed rounding is cosmetic; the underlying numbers are not rounded between steps, so chained results do not drift.