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Percent Decrease — Definition, Formula & Examples

Percent decrease is the percentage by which a value has gone down compared to its original value. It tells you the size of a reduction as a fraction of 100.

The percent decrease between an original value and a new, smaller value is the ratio of the difference (original minus new) to the original value, multiplied by 100.

Key Formula

Percent Decrease=Original−NewOriginal×100\text{Percent Decrease} = \frac{\text{Original} - \text{New}}{\text{Original}} \times 100
Where:
  • Original\text{Original} = The starting value before the decrease
  • New\text{New} = The ending value after the decrease

Worked Example

Problem: A jacket originally costs $80. It goes on sale for $60. What is the percent decrease in price?
Find the amount of decrease: Subtract the new price from the original price.
80−60=2080 - 60 = 20
Divide by the original: Divide the decrease by the original price.
2080=0.25\frac{20}{80} = 0.25
Convert to a percent: Multiply by 100 to express the result as a percentage.
0.25×100=25%0.25 \times 100 = 25\%
Answer: The price decreased by 25%.

Why It Matters

Sales, discounts, and markdowns all rely on percent decrease. Understanding it helps you compare deals when shopping and interpret data drops in science or economics classes.

Common Mistakes

Mistake: Dividing by the new value instead of the original value.
Correction: Always divide the change by the original (starting) value. The percent is relative to where you started, not where you ended up.

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