How to calculate the percentage difference between two numbers
✓ Verified in LibreOffice 25.8.7.3Compare two values symmetrically when neither is the "before" — two prices, two measurements, two vendors.
The formula
| App | Formula | Notes |
|---|---|---|
| Excel | =ABS(A2-B2)/((A2+B2)/2) | Symmetric: same answer whichever number comes first. Format as %. |
| Google Sheets | =ABS(A2-B2)/((A2+B2)/2) | Identical. |
| LibreOffice Calc | =ABS(A2-B2)/((A2+B2)/2) | Identical. |
How it works
Percentage DIFFERENCE divides the gap by the average of the two values: |80−100| / 90 ≈ 22.2%, and you get the same answer comparing 100 to 80. That symmetry is the point — use it when neither value is a baseline. When one IS the baseline (old vs new), use percentage CHANGE instead: (new−old)/old, which gives +25% from 80 to 100 but −20% from 100 to 80. Mixing up the two is a common source of "the percentages don't match" arguments.
Verified, not just documented
We ran =ROUND(ABS(A2-B2)/((A2+B2)/2),4) in LibreOffice 25.8.7.3 (headless, with forced recalculation) and it returned 0.2222 — exactly the expected result. Every formula here is confirmed by actually executing it.