Percentage Difference Calculator

Percentage difference compares two values without treating either one as “the original.” It is the right tool for comparing two measurements, two prices or an experimental result against a theoretical one. Enter any two values to get their difference as a percentage of their average.

Results

Formula

Because neither value is the reference, percentage difference divides by their average:
% Difference = |A − B| ÷ ((A + B) ÷ 2) × 100
Swapping A and B gives the same answer — that symmetry is the point.

How to use this calculator

  1. Enter the first value.
  2. Enter the second value (order does not matter).
  3. Press Calculate to see the difference, the average and the percentage difference.
Percentage Difference Calculator — how the calculation works, illustrated%
Percentage Difference Calculator — how the calculation works, illustrated

Worked example

Compare 40 and 60.

  1. Difference: |40 − 60| = 20.
  2. Average: (40 + 60) ÷ 2 = 50.
  3. 20 ÷ 50 × 100 = 40%.

Result: The percentage difference between 40 and 60 is 40%.

Frequently asked questions

Percentage difference vs percentage change — which should I use?

Use percentage change when one value is clearly the starting point (old vs new). Use percentage difference when comparing two values as equals, such as two measurements.

Why use the average as the denominator?

It keeps the comparison symmetric: the percentage difference between 40 and 60 equals that between 60 and 40, which is not true for percentage change.

Can percentage difference exceed 100%?

Yes, up to 200% — for example, comparing 10 and 100 gives a difference of about 164%.

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