How is percentage difference calculated?

Percentage difference = |A − B| ÷ ((A + B) ÷ 2) × 100. It divides the absolute difference by the average of the two values, so neither number is treated as the reference.

How is this different from percentage change?

Percentage change uses a starting value as the reference (divides by the original number), while percentage difference divides by the average of both numbers and is always positive.

Why does it use the average of the two numbers?

Dividing by the average makes the result symmetric — it does not matter which value you call A or B, and there is no "before" or "after". This suits comparing two measurements neither of which is a baseline.

Is the result always positive?

Yes. Because it uses the absolute difference |A − B|, the percentage difference is always zero or positive, regardless of the order you enter the numbers.

When should I use percentage difference versus percentage change?

Use percentage difference to compare two independent values, such as two lab measurements or two products. Use percentage change when one value is clearly the original and the other is the result.

What happens if both numbers are the same?

If A and B are equal, the absolute difference is zero, so the percentage difference is 0% — the two values are identical.

Is any data uploaded?

No — every calculation runs locally in your browser and nothing is sent to a server.

Percentage Difference Calculator

Percentage difference between two numbers

The percentage difference compares two values without treating either one as the reference point — useful when neither number is a “before” or “after”, such as comparing two measurements, two prices, or two test results. Because it is symmetric, the order you enter the numbers does not change the answer.

How it works

The calculator divides the absolute difference by the average of the two numbers, then scales to a percentage:

percentage difference = |A − B| ÷ ((A + B) ÷ 2) × 100

Using the average (rather than one of the values) is what makes the result the same whichever way round you enter the numbers, and it is always positive. Use percentage change instead when one value is clearly the original.

Example

Compare A = 40 and B = 60:

Absolute difference: |40 − 60| = 20
Average: (40 + 60) ÷ 2 = 50
Percentage difference: 20 ÷ 50 × 100 = 40%

A	B	Average	% difference
40	60	50	40%
90	100	95	10.53%
8	8	8	0%

Everything here runs in your browser — nothing is uploaded.