Percentage Change Calculator
One formula, both directions
A positive result is an increase, a negative result a decrease. The same calculation handles both, so there is no need to switch formulas depending on direction.
Example: 250 falling to 190.
((190 − 250) ÷ 250) × 100 = −24%
Increases and decreases are not symmetric
This is the single most important thing about percentage change, and it is widely misunderstood.
A 50% decrease followed by a 50% increase does not return you to the start. $100 falls to $50, then rises by 50% of $50 to $75 — still 25% below where you began.
The reason is that each percentage applies to a different base. The decrease applied to 100; the increase applied to 50.
| Decrease | Increase needed to recover |
|---|---|
| 10% | 11.1% |
| 25% | 33.3% |
| 50% | 100% |
| 80% | 400% |
The base determines the meaning
A percentage change is meaningless without knowing what it is measured against. "Sales up 200%" says nothing useful if sales were two units last month.
Small bases produce dramatic percentages, which is why percentage growth claims about new or tiny categories should be read alongside the absolute figures.
Where it's used
Price movements, investment returns, population and economic statistics, year-on-year business comparisons, and measuring experimental results against a control.