Percentage Difference Calculator
Find the relative difference between two values when neither is the "original." Order doesn't matter — you get the same result either way.
The Formula
The denominator is the average of the two values — that's what makes it symmetric. Swap A and B and you get the same answer.
Example
Comparing 80 and 100:
|80 − 100| = 20. Average = (80 + 100) / 2 = 90. 20 ÷ 90 × 100 = 22.22% difference.
Note: if you treated 80 as the original and asked "what changed?", you'd get 25% change. The different reference point is what makes the two calculations different.
When to Use Percentage Difference
Use percentage difference when you're comparing two equivalent things — two prices, two measurements, two competitors — and there's no clear "starting" value. Use percentage change when you have a before and after.
Common Questions
What's the difference between percentage difference and percentage change?
Percentage change needs a reference (the original). Percentage difference uses the average as the reference, making it order-independent. Use change for before/after. Use difference for side-by-side comparisons.
Is percentage difference always positive?
Yes, because it uses absolute value (|A − B|). It shows magnitude of difference, not direction.