Enter values and select Calculate.
Calculated result
Calculation steps
Formula and worked example
Percentage difference = |A − B| ÷ ((|A| + |B|) ÷ 2) × 100. If both values are zero, their difference is reported as 0%.
For 100 and 120, the absolute difference is 20 and the average magnitude is 110. The percentage difference is 20 ÷ 110 × 100, or about 18.1818%.
Calculations keep full internal precision and use controlled display precision with insignificant trailing zeros removed.
How to use percentage difference
Enter two finite values measured on the same basis.
Calculate to see the absolute difference, average magnitude, and symmetric percentage.
Swap the values if desired; the percentage difference will remain the same.
Use Percentage Change instead when one value is specifically the original baseline.
Zero and negative values
Two zero values are identical, so this calculator reports 0% difference.
Comparing zero with 10 produces 200%, not 100%, because their average magnitude is 5.
Negative inputs retain their signs in |A − B| while the denominator averages their absolute magnitudes.
The tool does not silently turn each entered value positive before finding their difference.
Difference versus change
Percentage difference treats both values equally and has no time or directional order.
Percentage change divides a signed change by an original reference value.
Choose the formula based on the meaning of the comparison, not merely which result looks smaller.
Methodology and limits
This deterministic browser-local tool strictly parses finite numbers and applies the formula stated above. It does not evaluate expressions, execute entered text, call a calculation API, or choose a contextual definition for you.