Percentage Decrease Calculator
Three common percentage decrease scenarios. Enter numbers below — results update instantly.
X decrease P% is what?
X = 100, P = 20%
Calculation:
100.00 × (1 - 20.00/100) = 80.00
X decrease what % is Y?
X = 200, Y = 160
Calculation:
(200.00 - 160.00) / 200.00 × 100% = 20.00%
What decrease P% is Y?
P = 25%, Y = 75
Calculation:
75.00 / (1 - 25.00/100) = 100.00
💡 Tip: Placeholder values show typical numbers – just overwrite them. Results update automatically.
About Percentage Decrease
A percentage decrease expresses the reduction of a value relative to its original amount. It is commonly used to describe discounts, depreciation, or declines in statistics.
The Three Scenarios
- X decrease P% is what? – Find the final value Y after a decrease:
Y = X × (1 - P/100). - X decrease what % is Y? – Find the percentage decrease P% that reduces X to Y:
P% = ((X - Y) / X) × 100%. - What decrease P% is Y? – Find the original value X before a decrease:
X = Y / (1 - P/100)(ensure P < 100).
Real‑World Examples
- Discount: A $100 item is on sale for 20% off. The sale price is 100 × (1 - 0.20) = $80.
- Population decline: A town's population dropped from 50,000 to 47,500. The decrease percentage is (50,000-47,500)/50,000 × 100% = 5%.
- Original price after discount: After a 15% discount, you pay $85. The original price was 85 / (1 - 0.15) = $100.
Important Notes
- Percentage decrease cannot exceed 100% (otherwise the result becomes negative).
- If Y is larger than X, the formula yields a negative percentage, indicating an increase instead.
- A 100% decrease reduces the value to zero.
Frequently Asked Questions
What if I have a 50% discount and then another 20% off?
Successive discounts are not additive. Apply the first discount, then the second on the new price. For $100, 50% off → $50, then 20% off → $40, total discount 60%.
How do I calculate the original price before a percentage decrease?
Use the formula: Original = Final / (1 - P/100). For example, if you paid $80 after a 20% discount, original = 80 / 0.8 = $100.
Can percentage decrease be applied to negative numbers?
Generally, percentage change is defined for positive numbers. For negative values, the interpretation may be ambiguous.