Calculate the percentage decrease between two values, or find the original or final value when you know the percentage. Enter any two of three fields and the third is computed automatically.
How to Calculate Percentage Decrease
Formula: (Initial − Final) / Initial × 100
Example: A jacket originally costs $80 and goes on sale for $68.
- Change: 80 − 68 = 12
- Percentage decrease: 12 / 80 × 100 = 15%
Reverse Calculation
Fill in any two fields and the calculator computes the third automatically.
- Initial + Final → Percentage decrease:
(Initial − Final) / Initial × 100
- Initial + Percentage → Final value:
Final = Initial × (1 − % / 100)
- Final + Percentage → Initial value:
Initial = Final / (1 − % / 100)
Example (finding original price): A TV sells for $680 after a 15% price cut. Original price = 680 / (1 − 0.15) = $800
Percentage Decrease vs Percentage Increase
These two calculations are not symmetric. A 20% decrease from 100 gives 80, but a 20% increase from 80 gives 96 — not 100. The base value changes between the two operations, so the same percentage applied in reverse does not undo the change.
Sources
Frequently Asked Questions
What is the formula for percentage decrease?
Percentage decrease = (Initial Value − Final Value) / Initial Value × 100. For example, if a price drops from $100 to $75, the decrease is (100 − 75) / 100 × 100 = 25%.
How do I find the original value if I know the final value and the percentage decrease?
Use the formula: Initial = Final ÷ (1 − Percentage / 100). For example, if a product costs $85 after a 15% discount, the original price was 85 ÷ (1 − 0.15) = $100.
Can the percentage decrease be more than 100%?
No. A value cannot meaningfully decrease below zero, so the maximum percentage decrease is 100% (which brings the value to zero). Any result of 100% or higher signals an input error.
What is the difference between percentage decrease and percentage change?
Percentage decrease measures only reductions and is always expressed as a positive number. Percentage change covers both directions — it is negative when the value falls and positive when it rises. The magnitude is the same; only the sign convention differs.