Money & Finance
Percentage Decrease Calculator
Percentage decrease measures how much a value has dropped, relative to where it started — used for price cuts, discounts, weight loss and any quantity shrinking over time.
The formula
decrease (%) = ((original value − new value) ÷ original value) × 100
Worked example
A price moves from $100 to $80:
(100 − 80) ÷ 100 × 100 = 20%
The price decreased by 20%.
Frequently asked questions
How do I calculate percentage decrease?
Subtract the new value from the original value, divide by the original value, then multiply by 100. Going from 100 to 80 is a 20% decrease.
Why isn't percentage decrease just the reverse of percentage increase?
Because the base changes direction. A 20% decrease from 100 to 80 isn't undone by a 20% increase — 80 increased by 20% is only 96, not 100. The two aren't symmetric.
What if the new value is actually higher?
The result will be negative, meaning the value increased rather than decreased. Use the Percentage Increase Calculator for a positive growth figure instead.