Percentage Difference vs Percentage Change: Which One Do You Need?

Percentage change

Percentage change compares a new value with an old one. Formula: (new minus old) divided by old, times 100. From 80 to 100, the change is 20 divided by 80, which is 25 percent up. From 100 to 80, the change is 20 percent down. The order matters.

Percentage difference

Percentage difference compares two values when neither is the reference. Formula: the absolute difference divided by the average of the two, times 100. For 80 and 100, that is 20 divided by 90, or 22.22 percent. Swapping the numbers gives the same answer.

Which should you use

• Price rose, sales fell, a before and after: percentage change.
• Two products or two measurements side by side: percentage difference.

Calculate both with the Percentage Difference Calculator. For simple percentages of a number, use the Percentage Calculator, and for sale prices the Discount Calculator.

Common mistakes

Do not divide by the new value when you want percentage change. Do not add percentage changes across steps, because each change applies to a different base. And remember that percentage change from zero is not defined.

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