How to Calculate Percentage Change (Increase and Decrease)
By Calqpro Editorial Team · April 20, 2026 · 4 min read
Percentage change comes up constantly — price changes, salary increases, weight loss progress, stock returns. The formula is simple but easy to apply wrong (especially the direction).
The Formula
The key: always divide by the original (old) value, not the new one. This is where most people make mistakes.
Examples
| Scenario | Calculation | Result |
|---|---|---|
| Price went from $80 to $100 | (100−80)÷80×100 | +25% increase |
| Salary from $60k to $72k | (72k−60k)÷60k×100 | +20% raise |
| Weight from 200 lbs to 185 lbs | (185−200)÷200×100 | −7.5% loss |
| Stock from $150 to $90 | (90−150)÷150×100 | −40% drop |
Common Mistake: Reversing the Direction
If a price increases 25% (from $80 to $100), it does NOT decrease 25% to get back to $80. It decreases 20%. Why? Because the base changes:
- +25% increase: $80 → $100 (base = $80)
- −20% decrease: $100 → $80 (base = $100)
This asymmetry trips up investors and negotiators constantly. A 50% drop requires a 100% gain to recover.
Percentage Change vs. Percentage Difference
Percentage change has a clear "before" and "after." Percentage difference compares two values without a direction — useful when neither value is the starting point. For difference, use the average of both values as the denominator: ((A−B) ÷ ((A+B)/2)) × 100.
Calculate any percentage change instantly
Use the Percentage Change Calculator →