Percentage calculator
Enter two valid numbers.
Key takeaways
- Three modes cover most quick desk checks without opening a spreadsheet.
- Percent change uses absolute old value in the denominator — standard finance definition.
- “X is what % of Y” answers share-of-total questions for dashboards.
- “X% of Y” answers discount and tax line previews.
- Mobile sliders and tall result type keep the answer readable outdoors.
Who built this
ContractorHQ is edited by Bernard Guido — 25+ years in trade operations and software. These utilities follow the same quality bar as our reviews: fast pages, honest disclosure, and tools that stay useful without selling your data.
Frequently asked questions
How is percent change calculated?
Percent change is new minus old divided by the absolute value of old, times one hundred. If the old value is zero the tool cannot divide and shows an invalid state because change from zero is undefined in this simple model.
Why four decimals in the “percent of” mode?
Many pricing and tax calculations need more than two decimals before rounding to currency. You can still round mentally when you copy the number out.
Is any data logged?
No. The calculation is performed locally. Refresh clears inputs unless your browser restores them.
Can I use commas as decimal separators?
Use a dot for decimals in this version. Thousands commas in the typed string are stripped before parsing so one thousand can be entered as one comma zero zero zero.