Formula
Percentage change = (new − original) ÷ |original| × 100Percentage difference = |a − b| ÷ ((a + b) ÷ 2) × 100 How it works
Percentage change tells you how big a change is compared with where you started. A positive result is an increase, a negative result is a decrease. Going from 50 to 65 is a 30% increase because the 15-unit rise is 30% of the starting 50.
The starting value matters. Rising from 50 to 65 is +30%, but falling back from 65 to 50 is only about −23.1%, because the second change is measured against the larger number 65. That is why a 50% loss needs a 100% gain to recover.
When neither number is the “before” value — say, comparing two prices from different shops — use the percentage difference instead. It divides by the average of the two numbers, so the answer is the same whichever order you enter them.
Frequently asked questions
What is the difference between percent change and percentage points?
Percentage points measure the plain gap between two percentages. An interest rate going from 4% to 5% is a rise of 1 percentage point, but a 25% increase in the rate itself.
Why can’t the original value be zero?
Percentage change divides by the original value. Dividing by zero is undefined, so any change starting from zero can’t be expressed as a percentage.
How do I reverse a percentage increase?
Divide by the multiplier rather than subtracting the same percentage. After a 25% increase (×1.25), divide by 1.25 to get back — that is a 20% decrease.