Percentage difference calculator

Local calculation

Compare two values on equal terms

Enter values in the same units, without currency symbols.

Example answer

Decimals

22.22%

Same both ways

Absolute gap

Same units as your inputs

80 vs 100: 22.22% difference.

Displayed results use your chosen decimal precision.

See the calculation

|80 − 100| ÷ ((80 + 100) ÷ 2) × 100 ≈ 22.22%

Absolute gap: |80 − 100| = 20. Average: 90.

Live resultsNo sign-upNumbers stay in your browser

Understand the comparison

How to calculate percentage difference

Percentage difference compares two non-negative values using their average as the baseline. Neither value is treated as the original. Enter two amounts in the same units above to see their percentage difference and absolute gap.

Percentage difference = |first − second| ÷ ((first + second) ÷ 2) × 100

The vertical bars mean absolute value: use the size of the gap, without a minus sign.

1. Find the gap

For 80 and 100, subtract the smaller value from the larger: 100 − 80 = 20.

2. Find their average

Add the values and divide by two: (80 + 100) ÷ 2 = 90.

3. Compare the gap

Divide the gap by the average, then multiply by 100: 20 ÷ 90 × 100 ≈ 22.22%.

Swapping 80 and 100 gives the same result. That symmetry is useful when comparing two quotes, measurements or quantities and neither one is a reference value. The absolute gap is 20 in the units you entered; the percentage difference is unitless.

Try a real comparison

Percentage difference examples

Select an example to load its numbers into the calculator. These comparisons use the average of the two values, not an original price or a target.

Compare two quotes

Quotes of 1,200 and 1,500 have an absolute gap of 300. Their average is 1,350, so the percentage difference is 22.22%.

Try the quote example

Compare measurements

Measurements of 48 and 52 have a gap of 4 and an average of 50: 8% difference. Check that both measurements use the same units.

Try the measurement example

Compare equal amounts

Two amounts of 75 have no gap: 0% difference. Equal positive values always produce zero.

Try equal values

Choose the right formula

Difference, change or percentage points?

What you mean	Baseline	Example
Percentage difference: compare two amounts equally	Average of both values	80 vs 100 → 22.22%
Percentage change: compare a new amount with its starting point	Original value	80 → 100 is a 25% increase
Percentage points: subtract two percentage rates	No division	20% → 25% is +5 percentage points

If a price rises from 80 to 100, use the percentage change calculator. Calling that rise a 22.22% increase would use the wrong baseline. Reversing the change, from 100 to 80, gives a 20% decrease; reversing a percentage-difference comparison still gives 22.22%.

If you are comparing a measurement with a known accepted value, you may need percentage error instead: the accepted value is the denominator. Use the formula specified by your assignment, experiment or reporting method. For a part of a total, or the difference between percentage rates, use the appropriate mode on our percentage calculator.

Percentage difference questions

Why do I divide by the average?

The average gives both values equal weight. Dividing by only the first value makes the result depend on which number comes first; that is a percentage change calculation instead.

What happens if one value is zero?

If one value is zero and the other is positive, the percentage difference is 200%. For example, the gap between 0 and 50 is 50 and their average is 25: 50 ÷ 25 × 100 = 200%. For non-negative values, this formula ranges from 0% to 200%.

What if both values are zero?

The formula has a zero denominator, so it is mathematically undefined. This calculator reports 0% by convention because the values are equal, and labels that case in the result. If your reporting rules require undefined or N/A, follow those rules.

Can I compare negative numbers?

This tool accepts zero or positive values. Negative values can make the average zero or produce misleading interpretations, so they are rejected. Choose a comparison method suited to your data before working with signed amounts.

How does rounding work?

Choose up to 0, 2, 4 or 8 decimal places. Display rounding does not change the values used for the calculation. A small non-zero result is marked approximately zero when necessary, with approximate values in the note. Very large numbers or long decimals can exceed browser precision.

Are my numbers saved?

The calculator performs its arithmetic in your browser. It does not send the entered values for calculation or save a calculation history. Copy answer places the result on your clipboard only when you select it.