Percentage decrease calculator
Measure decline from an original value to a lower new value.
What this calculator covers
Use this calculator to measure how much a value fell compared with its starting point.
It is built for markdowns, budget cuts, and other scenarios where the original value defines the full baseline.
Frequently asked questions
- Why does percentage decrease use the original value as the denominator?
- Because you are measuring how much of the starting amount was lost. Using the original as the baseline makes the percentage meaningful as a share of what you had before the decline.
- What is the formula for percentage decrease?
- Subtract the new value from the original value to find the amount lost, divide that by the original value, then multiply by 100. Written out: ((original − new) ÷ original) × 100.
- Is there a difference between percentage decrease and percentage change?
- They are the same calculation, but percentage decrease is typically framed for scenarios where the new value is lower than the original. If the new value were higher, you would call the result a percentage increase instead.
- Can both values be the same?
- Yes. If the original and new values are equal, the decrease is zero and the percentage result is 0%.
Tool
Run the calculation
Result
RESULT · DECREASE
â„–006
Primary result
20%
Moving from 100 to 80 is a 20% decrease.
- Amount lost
- 20
- Ending value
- 80
Step-by-step solution
- 1.Subtract the new value from the original value: 100 - 80 = 20.
- 2.Divide the change by the original value: 20 ÷ 100.
- 3.Convert the ratio to a percent: 20%.
Walkthrough
Visual walkthrough
Percentage decrease compares the amount lost to the original starting point.
01
Measure the drop
100 - 80 = 20
Start with the raw amount that disappeared between the two values.
02
Use the original as the baseline
20 ÷ 100
The original value stays in the denominator because it defines the full starting amount.
03
Convert to a percentage drop
Expressing the ratio as a percent makes the size of the decline easy to compare.
Decrease 20%