About the Percentage Difference Calculator
This percentage difference calculator compares two values when neither one is the obvious starting point — two prices from different stores, two lab measurements, two salaries or two products’ specs. It divides the gap between them by their average, so the answer is the same no matter which number you enter first.
Because people often mix up percentage difference and percentage change, the calculator also shows the percent change from A to B and from B to A. Use percentage change when one value clearly comes first (an old price and a new price); use percentage difference when the two are peers.
The symmetric formula needs the average of the two numbers to be non-zero, and percent change needs a non-zero starting value; when either would divide by zero the calculator shows “Undefined” rather than a number. If one value is positive and the other negative the result can exceed 200% and is rarely meaningful, so compare absolute amounts instead.
With the default inputs, the percentage difference is 28.5714%. Change any value above to recalculate instantly.
How to use the percentage difference calculator
- 1Enter the first value (A).
- 2Enter the second value (B) — the order does not matter.
- 3Read the percentage difference.
- 4If one value is clearly the starting point, use the percent change figures instead.
Formula and method
The absolute difference between the two numbers is divided by their average (arithmetic mean) and multiplied by 100. Using the average as the reference makes the result symmetric: swapping A and B gives the same percentage, which is what you want when neither number is the “original”.
Percent change instead divides by the starting value: (new − old) ÷ |old| × 100. It gives different answers depending on direction — 150 to 200 is +33.3%, but 200 to 150 is −25% — so it suits before-and-after comparisons, not peer comparisons.
- A, B
- The two values being compared
- (A + B) ÷ 2
- Their average, used as the reference
Worked examples
Two quotes: $150 vs $200
The quotes differ by $50 and average $175, so the percentage difference is 50 ÷ 175 × 100 = 28.57%. As a change, $150 → $200 is +33.3% while $200 → $150 is −25%.
10 vs 20
The difference of 10 divided by the average of 15 gives 0.6667, or a 66.67% difference.
Two lab readings: 49.5 and 50.5
The readings differ by 1.0 around an average of 50, so they are 2% apart — useful for judging whether repeat measurements agree.
Opposite values: 5 and −5
The average of 5 and −5 is 0, so dividing the gap of 10 by it is impossible and the percentage difference is Undefined. Percent change still works because each starting value is non-zero: (−5 − 5) ÷ 5 = −200%, and (5 − (−5)) ÷ |−5| = +200%.
Frequently asked questions
How do you calculate percentage difference?+
Take the absolute difference between the two numbers, divide by their average and multiply by 100. For 40 and 60: |40 − 60| ÷ 50 × 100 = 40%.
What is the difference between percentage difference and percentage change?+
Percentage change measures growth from an original value and depends on direction. Percentage difference compares two peer values relative to their average and is the same whichever way round you put them.
Why is 100 to 150 a 50% increase but 150 to 100 only a 33% decrease?+
Each percent change is measured against a different starting value (100 versus 150). Percentage difference avoids this by using the average, 125, giving 40% either way.
How do I find the difference between two percentages?+
Subtracting them gives the difference in percentage points (45% − 40% = 5 points). The relative percentage difference is 5 ÷ 42.5 = 11.8%. Say which one you mean to avoid confusion.
Can percentage difference be more than 100%?+
Yes. For positive numbers it can approach 200% as one value gets close to zero. For example, 1 and 9 differ by 8 ÷ 5 = 160%.