Percentage Difference Calculator
Compute percentage difference, percent change from A to B, or percent error against a true value.
Quick answer
Percentage difference compares two values symmetrically: |A - B| / ((|A| + |B|) / 2) x 100. Percent change from A to B is (B - A) / |A| x 100, and percent error is |A - B| / |B| x 100.
Percentage Difference Calculator
First value, old value or measured value.
Second value, new value or true value.
Percentage Difference
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Absolute Difference |A − B|
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Average of A and B
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All Three Measures for A and B
| Measure | Formula | Result |
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Assumptions & method
- Percentage difference = |A − B| ÷ ((|A| + |B|) ÷ 2) × 100. It is symmetric, so swapping A and B gives the same value. If A and B are both 0 the difference is 0%.
- Percent change from A to B = (B − A) ÷ |A| × 100. Undefined when A = 0. A negative result is a decrease.
- Percent error = |A − B| ÷ |B| × 100, where A is the measured value and B the true value. Undefined when B = 0.
- The average of A and B is (A + B) ÷ 2.
- Percentages are shown rounded to two decimals. Results describe only the two numbers you enter.
Results are estimates based on the figures you enter. They are not guarantees and not financial advice.
Three ways to compare two numbers
There is more than one correct way to express how far apart two numbers are as a percentage, and the right one depends on the question. Percentage difference divides the gap by the average of the two values, so it is symmetric and works when neither number is the reference. Percentage change divides by the starting value and shows direction, which suits growth and decline. Percent error divides by the true or accepted value and checks how far a measurement is off. This calculator reports all three for the same pair of numbers, with the one you select shown first.