How this calculator works
Percent change compares the change to the starting value. Percent difference compares two values with no “before” and “after”, using their average as the base, so it gives the same answer whichever order you enter them.
Percent change = (New − Old) ÷ |Old| × 100
Percent difference = |A − B| ÷ ((|A| + |B|) ÷ 2) × 100
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Old value (from) | 80 |
| New value (to) | 100 |
| Result | Value |
|---|---|
| Percentage increase | 25 % |
| Change | 20 |
| Percent difference (symmetric) | 22.22 % |
| New value as % of old | 125 % |
| Multiplier | 1.25 × |
Step by step:
- Change = 100 − 80 = 20
- ÷ |80| = 0.25
- × 100 = 25%
Common mistakes to avoid
- Dividing by the new value instead of the old one.
- Calling a change from 4% to 6% a “2% increase” — it is 2 percentage points, or a 50% increase.
Frequently asked questions
What is the percent increase from 80 to 100?
(100 − 80) ÷ 80 = 25%.
Why does a 25% rise need a 20% fall to undo it?
Because the fall is measured from the larger number: 100 back to 80 is a drop of 20 out of 100.