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Percentage Decrease Calculator
Calculate the percentage drop or discount between initial and final values.
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How this calculator works
Calculate discounts, price drops, or losses using our free percentage decrease calculator. This tool measures the relative decline from a starting initial value to an ending final value. Enter your parameters to see the exact percentage drop and the mathematical steps involved.
- Method
- Relative decrease from a positive baseline
- Source
- U.S. Bureau of Labor Statistics — Calculating percent changes
- Last reviewed
- 2026-08-27
Method limitations
- Starting value must be positive.
- Ending value must be from zero through the starting value.
- Values must use the same quantity and unit.
- The result measures relative arithmetic change, not causation or financial loss.
Engine-backed example
Percentage decrease from a positive baseline: worked example
What is the percentage decrease from 200 to 120?
- Starting value
- 200
- Ending value
- 120
Percentage Decrease40.00%
- Absolute Loss
- 80
- Starting Value
- 200
- Ending Value
- 120
The absolute decrease is 80. Dividing 80 by the starting value, 200, and multiplying by 100 gives a 40% decrease.
Trust and review
Who created and reviewed this calculator?
- Author
- CalcOS Editorial TeamResponsible for percentage-change terminology, examples, assumptions, and search-intent clarity.
- Reviewed by
- CalcOS Scientific ReviewTechnical review of percentage-decrease arithmetic, positive-baseline requirements, boundaries, rounding, engine parity, and interpretation.
- Substantive review date
- 2026-08-27Positive starting values, non-negative non-increasing ending values, absolute decrease, percentage decrease, invalid-state handling, worked-example parity, and stated limitations.
Sources
- U.S. Bureau of Labor Statistics — Calculating percent changes
- U.S. Bureau of Labor Statistics — Index Numbers and Percent Changes
Assumptions used by this calculator
- The starting and ending values measure the same quantity in the same units.
- The starting value is finite and strictly greater than zero.
- The ending value is finite, non-negative, and no greater than the starting value.
- Percentage decrease equals (starting value − ending value) divided by starting value, multiplied by 100.
- A zero ending value represents a 100% decrease under this arithmetic contract.
- Use an increase or general percentage-change method when the ending value is higher or the baseline is zero or negative.