Percentage Calculator
Calculate percentages, proportions, reverse-calculate original values, rate of change, and percentage increases or decreases, with explicit handling of zero denominators.
How to use the percentage calculator
The entered value is calculated only in the current browser and will not be uploaded or saved.
Select issue type
Can calculate percentages, ratios, reverse-engineer the original value, change rates, or increase and decrease by percentage.
Enter values
Enter a limited number by label; supports decimals and negative numbers.
Read results
The result will show the formula and a decimal with moderate precision, which can be copied for verification.
Limitations and Notes
- When the divisor or original value is 0, the percentage, reverse calculation, and change rate have no finite result, and the page will show an explicit error.
- Results are calculated using JavaScript floating-point numbers; very large numbers, very small numbers, and financial amounts may have rounding errors.
- This page is for mathematical conversion only and does not include tax, compound interest, regulatory, or commercial interpretations.
FAQ
What is the increase from 0 to 10?
When the original value is 0, the traditional percentage increase or decrease is undefined, so infinity will not be shown.
Can negative numbers be calculated?
Yes, but the meaning of gain/loss for negative bases may differ from business conventions; please explain it in context.
Why does the result have decimals?
The page preserves meaningful precision and removes unnecessary trailing zeros, without forcing rounding to an integer.