What is percentage difference?
It measures how different two values are relative to their average.
Percentage Difference Calculator
Compare two values without treating either as the original—useful when both are measurements.
Enter two values
Provide value A and value B to compute the percentage difference.
About this calculator
How to use Percentage Difference Calculator, plus the formulas and logic behind the results.
Tool description
Percentage difference divides the absolute gap by the average of the two values. Neither value is treated as a baseline.
How to use
- Enter the first value.
- Enter the second value.
- Select Calculate to view the percentage difference.
- Review the absolute difference and average used.
Formulas & reference
Percentage difference = |A − B| ÷ ((A + B) / 2) × 100
When to use it
- Comparing two lab readings
- Neither value is the “true” original
- Result is always non-negative
- Different from percent increase/decrease
Calculation logic
The absolute difference is divided by the mean of the two inputs and scaled by 100. A zero average (A = −B) is rejected.
Unlike percent change, percentage difference is symmetric: swapping A and B does not change the result.
Percentage Difference Calculator FAQ
Common questions about this calculator and how to use the results.
How is it different from percent change?
Percent change uses one value as the baseline; percentage difference treats both equally.
Is the result signed?
No. Absolute difference makes the percentage non-negative.
What if A equals B?
The percentage difference is 0%.
Why can the average not be zero?
If A = −B, the average is zero and the formula is undefined.
Does order matter?
No. Swapping A and B yields the same percentage difference.