Percentage Difference Calculator
The Percentage Difference Calculator compares two numbers as a percent of their average. It is the standard way to compare two measurements of the same thing, such as two prices or two estimates, without picking one as the 'original'.
What this means
Unlike percentage change (which needs an original value), percentage difference uses the average of the two numbers as its base, so the result is the same whichever number you enter first.
How we calculate it
Formula
Difference % = |A − B| ÷ (|A + B| ÷ 2) × 100.Worked example
Compare 100 and 120:
- 1Average = (100 + 120) ÷ 2 = 110
- 2|100 − 120| ÷ 110 = 20 ÷ 110
- 320 ÷ 110 × 100 ≈ 18.18%
Important assumptions
- Percentage difference is best for comparing two measurements of the same kind.
Frequently asked questions
Percentage difference vs percentage change?
Change needs an original and a new value and describes movement over time. Difference compares two values symmetrically using their average.
Why is the result the same regardless of order?
Because both the numerator (|A − B|) and the denominator (the average) are symmetric — swapping the inputs changes neither.
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