ToolwebHow to use this tool
- Choose a percentage amount, a part-to-whole ratio, or a percentage change.
- Enter the amount and percent, the part and whole, or the original and new values.
- Inspect the formula, difference and exact ratio as well as the main result.
Measure a change from 80 to 100
- Input and settings
- Percentage change; original 80; new 100
- Result
- 25% change; difference 20
The absolute difference of 20 and the percentage change of 25% describe different things.
The denominator defines the question
A percentage of an amount uses amount × percent ÷ 100. A part as a percentage instead uses part ÷ whole × 100. Separate modes keep those denominators visible rather than asking you to infer the meaning of two unlabeled numbers.
Percentage change uses (new - original) ÷ original × 100. A zero original value makes the ratio undefined and is rejected. Negative base values are processed literally, so interpret the sign in the context of your data.
Separate the visual from the value
The preview bar depicts only the 0–100% interval. A negative value or a value above 100% can still be calculated, but the bar does not expand to portray the entire range; read the numeric output for the actual result.
Decimal inputs are converted to fractions before ratio arithmetic; the decimal display may be rounded. Percentage-point differences, tax rules, compounding and currency conversions are not automatically inferred.
Common questions
Does a 10% decrease followed by a 10% increase cancel out?
Generally no, because the base changes between steps. Enter the actual base amount for each step separately.
Can the result exceed 100%?
Yes. A part larger than the whole produces more than 100%. A full visual bar does not cap the numeric output.