Percentage Decrease Calculator
The percentage decrease calculator has two modes. In the first mode, you enter an original value and a percentage, and the calculator returns the new value after a percentage decrease is applied. For example, if an item costs 100 dollars and the price decreases by 20%, the new price is 80 dollars. In the second mode, you enter the original value and the new value, and the calculator returns the percentage decrease between them. For example, if a quantity was 100 and is now 75, the percentage decrease is 25%. Percentage decrease is commonly used to describe price discounts, sales reductions, weight loss, and other downward changes. It provides a relative measure of change that is easier to compare across different scales than absolute change. The calculator uses the formulas: new value = original * (1 - percentage / 100) and percentage decrease = ((original - new) / original) * 100.
Percentage decrease formula
New value = original value * (1 - percentage / 100)
Absolute decrease = original value - new value
Percentage decrease = ((original - new) / original) * 100
Examples
| Original | Percentage decrease | New value | Absolute decrease |
|---|---|---|---|
| 100 | 20% | 80 | 20 |
| 200 | 50% | 100 | 100 |
| 1,000 | 10% | 900 | 100 |
| 150 | 25% | 112.50 | 37.50 |
| 500 | 75% | 125 | 375 |
Percentage decrease calculator: frequently asked questions
What is a percentage decrease?
A percentage decrease is a measure of how much a value has fallen relative to its original value, expressed as a percentage. For example, if a price drops from 100 to 80, the percentage decrease is 20%. The formula is: percentage decrease = ((original value - new value) / original value) * 100.
How do I calculate a percentage decrease?
There are two common scenarios. First, if you know the original value and the percentage decrease, find the new value using: new value = original value * (1 - percentage / 100). For example, a 100 dollar item with a 20% discount costs 100 * 0.80 = 80 dollars. Second, if you know the original and new values, find the percentage decrease using: percentage decrease = ((original - new) / original) * 100.
Can percentage decrease be more than 100%?
No. A percentage decrease cannot exceed 100% because that would result in a negative value. A 100% decrease means the value becomes zero. If a value would drop below zero from the calculated percentage, that is not a valid percentage decrease but rather complete elimination.
What is the difference between percentage decrease and absolute decrease?
Absolute decrease is the raw difference: original value - new value. Percentage decrease expresses this as a percentage of the original value. For example, both 100 to 90 and 1,000 to 900 have an absolute decrease of 10, but the first has a 10% decrease and the second has a 1% decrease.
How is percentage decrease different from percentage change?
Percentage decrease specifically measures downward change, so it is always positive (the result of the calculation). Percentage change can be positive or negative to indicate direction. A 20% decrease is the same as a -20% percentage change.
Official sources
- Standard mathematical formula for percentage decrease.
- NIST Special Publication 330: The International System of Units.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.