Try it
Old and new values share one scale. Negative values extend below zero.
Change+25%
DirectionIncrease
Understand the result
What's going on
Saying a value “went up by 20” means something different depending on where it started. Percentage change fixes that - it always measures the change relative to where you began, so a jump from 80 to 100 and a jump from 8,000 to 10,000 both read the same way: up 25%.
The formula
% change = (new − old) / old × 100
A negative result means the value decreased.
Show the derivation, mnemonic, and worked example
Build it up
First find the plain change - new value minus old value. That number alone doesn’t mean much without context, so divide it by the old value to turn it into a fraction of where you started. Multiply by 100 to read that fraction as a percentage.
Worked example
Worked example
Old = 80, New = 100
(100 − 80) / 80 × 100
= 25% increase
