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How to Calculate Percentage Difference

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Direct answer

Take the absolute gap between two peer values and divide by their average magnitude. This answers how far apart the values are relative to a shared scale.

Formula and method

|A−B| / ((|A|+|B|)/2) × 100

This page must show the formula exactly as the calculator or worked method uses it. Inputs remain unrounded during the calculation; rounding applies only to the displayed answer unless a domain-specific rule requires otherwise.

Step-by-step calculation

  1. Confirm neither value is the designated baseline.
  2. Use the same units.
  3. Calculate the absolute gap.
  4. Calculate the average magnitude and divide.

Worked examples

12 and 15

Gap 3, average 13.5, difference 22.222…%.

120 and 100

Gap 20, average 110, difference 18.1818…%.

Order

Reversing either pair leaves the result unchanged.

Interpretation and edge cases

  • Some disciplines use a reference or control denominator instead; then the calculation is relative difference or percent error, not this symmetric formula.
  • Document the formula in reports.
  • Round only at the end.

Frequently asked questions

Which value is the denominator?

Neither alone; use their average magnitude.

Why absolute values?

They prevent sign cancellation in the scale denominator.

Can I compare dollars and euros directly?

Only after converting them to a common unit and time basis.

Sources and transparency

The formulas and examples were evidence-checked on 2026-09-10. This is educational mathematical content. It does not replace a field-specific standard, accounting policy, laboratory method, contractual definition or professional judgment. CalculatorGeek should display a named human reviewer only after a real reviewer has completed and documented that review.

Use this resource

1 available tool
Open the Percentage Difference CalculatorRun the calculation with your own inputs, then return here to interpret it.

Keep exploring

4 available tools
Percentage Difference vs Percent ChangeChoose percentage difference for peer values or percent change for an old-to-new comparison. See formulas, symmetry and examples.Percentage Difference With Zero and Negative ValuesCalculate percentage difference with zeros and negative values using an average-magnitude denominator and explicit edge-case rules.Relative Percent Difference for Duplicate MeasurementsCalculate relative percent difference for duplicate measurements and understand when RPD is useful, symmetric and incomplete without uncertainty context.Percentage Points vs Percentage DifferenceCompare percentage-point difference with relative percentage difference when both inputs are percentages.