MasterTool

Percent Difference Calculator

Calculate percent difference instantly in your browser.

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What this tool does

Calculate percent difference instantly in your browser. Not the same as percentage change: percent difference is symmetric — swapping the two values gives the same answer.

How to use the Percent Difference Calculator

  1. Enter or select first value.
  2. Enter or select second value.
  3. Read the calculated result; change any measurement to compare alternatives.

Formula

percent difference = |a − b| ÷ ((a + b)/2) × 100 — the difference relative to the average of the two values, so neither value is treated as the 'original'.
a
First value
b
Second value

Not the same as percentage change: percent difference is symmetric — swapping the two values gives the same answer.

Worked example

For percent difference calculator, the following measurements illustrate the exact method: First value: 80; Second value: 100.

Inputs

  • First value80
  • Second value100

Result

  • Percent difference (%)22.22
  • Absolute difference20
  • Average of the two values90

Results explained

Percent difference (%)
Percent difference (%) from the formula above. Not the same as percentage change: percent difference is symmetric — swapping the two values gives the same answer.
Absolute difference
Absolute difference from the formula above. Not the same as percentage change: percent difference is symmetric — swapping the two values gives the same answer.
Average of the two values
Average of the two values from the formula above. Not the same as percentage change: percent difference is symmetric — swapping the two values gives the same answer.

Frequently asked questions

percent difference = |a − b| ÷ ((a + b)/2) × 100 — the difference relative to the average of the two values, so neither value is treated as the 'original'.

Not the same as percentage change: percent difference is symmetric — swapping the two values gives the same answer.

Where mathematically meaningful, yes. Fields specify permitted ranges and undefined operations display an error.

Exact integer calculations use safe integers; decimal calculations use browser floating point, so small rounding differences can occur.

All values remain in your browser and are never uploaded.