Percentage Difference Calculator

A percentage difference calculator answers one question. How far apart are two numbers? It treats both values equally, using their average as the base, so swapping the inputs always gives the same answer.

Use it for two numbers with no natural order, such as two store prices. It is free and instant.

1. Type your first value into the Value A field.
2. Type your second value into the Value B field. Order does not matter.
3. Press Calculate, or press Enter. The result appears with the steps.
4. Press Reset to clear the form.

Two zeros give an undefined answer. One zero always gives 200%.

Did one value come before the other? If yes, you want change. Use our Percentage Change Calculator for a before and after.

Take 80 and 100. The difference is 22.22%, the change is 25% from 80 to 100 and 20% from 100 to 80. Note that 22.22% falls between the two.

A 25% increase followed by a 25% decrease does not return you to the start. $100 becomes $125, then $93.75. Directional percentages do not cancel out.

Percentage Difference = |A − B| / ((A + B) / 2) × 100.

The 4-Step Method

1. Find |A − B|, the absolute difference.
2. Find (A + B) / 2, the average.
3. Divide the first by the second.
4. Multiply by 100.

With 10 and 15: difference 5, average 12.5, 5 / 12.5 × 100 = 40%.

Why the Formula Uses the Average

Dividing by one value picks a favorite. For 10 and 15, a base of 10 gives 50% but a base of 15 gives 33.33%. Only the average treats both values the same.

Use it when two numbers have equal standing and neither is the baseline.

• Same product at two stores.
• Two lab instruments measuring one sample.
• An experimental result versus a theoretical value.
• Peer metrics of equal rank.

Do not use it to track change over time. That is a before-and-after job for percentage change. The gap between 40% and 55% is 15 percentage points. For part-to-whole questions, our percentage calculator does the standard job.

Why the Answer Is Never More Than 200%

The average is always at least half the absolute difference, so the result tops out at 200%. One zero value gives 200%. Identical values give 0%.

Negative Numbers and Zero

The standard formula works best with two positives. With negatives, use |A − B| / ((|A| + |B|) / 2) × 100. For −40 and −60 that gives 40%.

In Excel or Google Sheets, use =ABS(A2-B2)/AVERAGE(A2,B2). ABS gives the absolute difference and AVERAGE gives the midpoint.

1. Type your first value in cell A2 and your second in cell B2.
2. In cell C2, type =ABS(A2-B2)/AVERAGE(A2,B2).
3. Format C2 as a percentage.

10 and 15

Difference 5, average 12.5: 5 / 12.5 × 100 = 40%.

80 and 100

Difference 20, average 90: 20 / 90 × 100 = 22.22%.

Readings 48.2 and 50.5

Difference 2.3, average 49.35: 2.3 / 49.35 × 100 = 4.66%.

Prices $899 and $949

Difference 50, average 924: 50 / 924 × 100 = 5.41%.

• Using percentage change for values with no natural order.
• Dividing by one value instead of the average.
• Mixing up percentage points and percentage difference.
• Expecting a direction. The answer is always positive.
• Forgetting the both-zero case.