How to calculate percent change
The formula is: ((new value − original value) / |original value|) × 100. A positive result means an increase; negative means a decrease. For example, going from 80 to 100 is a 25% increase. Going from 100 to 80 is a 20% decrease.
Percent change formula
% change = ((new − original) / |original|) × 100. Note that a 25% increase followed by a 20% decrease returns to the original — percentage changes are not symmetric. An increase from X to Y is a different percentage than the decrease from Y back to X.
FAQ
What is the difference between percent change and percentage points?
Percent change is relative to the original value. Percentage points are absolute differences between two percentages. If a rate goes from 10% to 15%, that is a 5 percentage point increase, but a 50% percent change.
Why can't the original value be zero?
Percent change is defined as the change divided by the original value. Division by zero is mathematically undefined — there is no meaningful way to express 'percent change from zero.'