How it works
Percent change measures how much a value grew or shrank relative to where it started. A positive result is an increase and a negative result is a decrease.
Because the starting value is the reference, percent changes are not symmetric: going from 50 to 75 is a 50% increase, but going back from 75 to 50 is a 33.33% decrease.
Formula
percent change = (new − original) ÷ |original| × 100
Questions people ask
Why does a 50% drop need a 100% gain to recover?
After a 50% drop, 100 becomes 50. To get from 50 back to 100 you must add 50, which is 100% of the new, smaller base.
What is the difference between percent change and percentage points?
If a rate goes from 4% to 5%, that is a 1 percentage-point increase but a 25% percent change, because 1 is 25% of 4.
Can I calculate percent change from zero?
No. Dividing by a starting value of zero is undefined, so the change can only be described in absolute terms.