The Short Version
Use percentage change when there is a clear before-and-after direction. Use percentage difference when you compare two values without treating one as the starting point.
Percentage Change Formula
Percentage change = (New − Old) ÷ Old × 100
Example: price goes from $80 to $100.
($100 − $80) ÷ $80 × 100 = 25% increase
This formula is directional. $100 to $80 is a 20% decrease, not the same result.
Percentage Difference Formula
Percentage difference = |A − B| ÷ ((A + B) ÷ 2) × 100
Example: compare $80 and $100.
20 ÷ 90 × 100 = 22.22% difference
This formula is symmetric. Comparing 80 to 100 gives the same result as comparing 100 to 80.
Side-by-Side Examples
| Values | Percentage Change | Percentage Difference |
|---|---|---|
| 80 → 100 | +25% | 22.22% |
| 100 → 80 | -20% | 22.22% |
| 50 → 75 | +50% | 40% |
| 75 → 50 | -33.33% | 40% |
Which One Should You Use?
Use percentage change for rent increases, salary raises, weight loss, price changes, investment returns, or any old-to-new comparison.
Use percentage difference for comparing two measurements, two estimates, two prices from different stores, or two independent results.
For old-to-new changes only, the percentage increase calculator is faster.