Percentage decrease measures how much a value has dropped relative to its starting point. A product marked down from $200 to $150 has decreased by 25% — the formula is (200 − 150) ÷ 200 × 100. Enter the original value and the new value to get both the absolute difference and the percentage drop.
The Percentage Decrease Formula
- Subtract the new value from the original value
- Divide the result by the original value
- Multiply by 100 to convert to a percentage
- Example: (200 − 150) ÷ 200 × 100 = 25% decrease
Percentage Decrease vs. Percentage Points
A drop from 20% to 15% is a 5 percentage point decrease, but a 25% relative decrease — (20 − 15) ÷ 20 × 100. These two measures answer different questions. Percentage points describe the absolute shift on the scale, while percentage decrease describes the size of the change relative to where it started. Mixing them up is one of the most common errors in data reporting.
When the Result Exceeds 100%
Percentage decrease can exceed 100% when the new value crosses zero. A stock going from $100 to −$20 is a 120% decrease. This happens in accounting (net income turning negative), physics (temperature crossing zero on some scales), and inventory tracking (backorders creating negative stock). The formula still works — just note that a decrease beyond 100% means the quantity reversed direction.
Percentage Decrease vs. Percentage Difference
Percentage decrease uses the original value as the denominator and assumes a drop. Percentage difference uses the average of both values and works in either direction. Use decrease when there is a clear before-and-after relationship — a price was $80, now it is $60. Use difference when comparing two independent measurements where neither is the baseline.
FAQ
Q: Can percentage decrease be more than 100%?
A: Yes. If the new value is zero or negative while the original is positive, the result exceeds 100%. For example, going from 100 to −50 is a 150% decrease.
Q: What is the difference between percentage decrease and discount?
A: They use the same formula. A discount is a percentage decrease applied to a price. Original price $80, sale price $60: (80 − 60) ÷ 80 × 100 = 25% discount.
Q: Why does my percentage decrease not match the percentage point change?
A: Because they measure different things. A conversion rate dropping from 20% to 15% fell by 5 percentage points, but the rate itself decreased by 25% relative to where it started. Percentage decrease is relative; percentage points are absolute.