What is Percentage Difference?
Percentage difference calculates the relative difference between two values using their average as the reference point. Unlike percentage change, it's symmetric - swapping the values gives the same result.
Formula
Percentage Difference = (|Value2 - Value1| / ((Value1 + Value2) / 2)) x 100
Key Characteristics
- Always positive (uses absolute values)
- Symmetric (order doesn't matter)
- Uses average as reference
- Best for comparing similar quantities
Examples
Example 1: Compare 80 and 100
Average = (80 + 100) / 2 = 90
Difference = |100 - 80| = 20
Percentage Difference = (20 / 90) x 100 = 22.22%
Example 2: Compare test scores of 85 and 92
Average = (85 + 92) / 2 = 88.5
Difference = |92 - 85| = 7
Percentage Difference = (7 / 88.5) x 100 = 7.91%
When to Use
Use percentage difference when comparing two values without a clear "old" and "new" - for example, comparing measurements, test results, or prices from different sources.
Quick Tips
- Double-check your inputs for accurate results
- Use parentheses to clarify order of operations
- Results are rounded — consider significant figures
Frequently Asked Questions
Percentage change uses the original value as base; percentage difference uses the average of both values.
Yes, it uses absolute values so it's always positive.
When comparing two values without a clear reference point or direction of change.
Yes, when the values are very different relative to their average.
Using the average makes the calculation symmetric and fair to both values.