Percentage increase and decrease calculator
Percentage change is always measured against the starting value, which is why going up 50% and back down 50% does not return you to where you began.
Percentage change
25%
- Absolute difference
- 20
- Change needed to get back
- -20 %
- Multiple of the original
- 1.25
Show the working
- From = 80
- To = 100
- Absolute difference = 100 - 80 = 20
- Percentage change = 80 != 0 ? 20 / abs(80) * 100 : 0 = 25
- Change needed to get back = 100 != 0 ? -20 / abs(100) * 100 : 0 = -20
- Multiple of the original = 80 != 0 ? 100 / 80 : 0 = 1.25
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- percentage change = (new - old) / |old| x 100
Rising from 80 to 100 is a 25% increase; falling from 100 back to 80 is a 20% decrease. The base changed, so the percentages differ.
Frequently asked
Why are percentage increase and decrease not symmetric?
Because each is measured against its own starting value. A 25% rise is reversed by a 20% fall.