1
Enter two values
Add the two non-negative amounts you want to compare. Neither is treated as the original.
Math
Free tool
Percentage Difference Calculator
Compare two values and calculate their percentage difference relative to their average.
No account needed · Calculated in your browser
Calculate percentage difference
Enter two non-negative values. Neither value is treated as the starting value.
Result
How to use this calculator
Three steps to an answer you can interpret.
2
Calculate the difference
The tool divides their absolute gap by their average.
3
Read the percentage
A larger percentage means the values are farther apart relative to their size.
Understand the result
Compare two non-negative values symmetrically using their average as the reference.
Percentage difference compares two values without declaring either one to be the original. It measures their absolute separation relative to their average.
Formula
|A − B| ÷ ((A + B) ÷ 2) × 100.
Worked example
For 80 and 100, the absolute difference is 20 and the average is 90, so the percentage difference is about 22.22%.
Changing the input order leaves the percentage difference unchanged.
Why percentage difference is symmetric
Swapping A and B does not change the absolute difference or their average, so A versus B gives the same percentage difference as B versus A.
Zero values
If one value is zero and the other is positive, the percentage difference is 200%. Two zero values are undefined because their average is zero.
Percentage difference vs percentage change
Percentage difference is symmetric. Percentage Change Calculator is directional and divides by an original value. For basic percentage questions, use the Percentage Calculator.
More useful tools
View allFrequently asked questions
Does input order matter?
No. The result is symmetric.
Can one value be zero?
Yes, provided the other is greater than zero.