Percentage Difference Calculator
Find the percentage difference between two numbers using their average, and see how it differs from percentage change. Step-by-step working included.
Percentage difference
Two nonnegative values measured in the same units. At least one must be positive; two zeros have no nonzero average. Negative measurements need a separately defined comparison convention and are not supported.
Formula checked · NumberSwift · Review process
How this calculator works
Percentage difference compares two values without selecting one as the original. It divides their absolute gap by their average, so swapping the values gives the same answer. This is useful for comparing two measurements of the same kind. Percentage change instead answers how much an original value grew or fell.
Formula
Percentage difference = |A − B| / ((A + B) / 2) × 100%.
Assumptions & limitations
Two nonnegative values measured in the same units. At least one must be positive; two zeros have no nonzero average. Negative measurements need a separately defined comparison convention and are not supported.
Worked example
For 80 and 100, the gap is 20 and their average is 90. The percentage difference is 22.2222%. The percentage change from 80 to 100 is 25%, which answers a different question.
Useful next calculations
Choose a related task to continue with the right assumptions:
Common questions
Does changing the input order change the result?
No. The absolute gap and average are both symmetric.
Can I compare zero with a positive value?
Yes. For example 0 and 10 differ by 200% relative to their average of 5. Two zero inputs are undefined.
When should I use percentage change?
Use change when there is a starting amount and a later amount, such as a price before and after an increase.