Percentage Difference Calculator

Compare two numbers with our Percentage Difference Calculator.

Value A

Value B

How it works: Enter two values to compare them. Percentage difference is |A − B| ÷ ((|A| + |B|) ÷ 2) × 100, so neither value is treated as the starting point. Percent change from A to B is shown alongside it.

Overview

Compare two numbers with our Percentage Difference Calculator. Enter any two values to see the percentage difference between them, the absolute difference, and the percent change from the first value to the second. Percentage difference uses the midpoint formula, |A − B| ÷ ((|A| + |B|) ÷ 2) × 100, so it gives the same result whichever value you enter first. Use it to compare prices, measurements, or survey results when neither number is the obvious starting point. If you are measuring growth from an original value, use the percent change result instead. Results are displayed to two decimal places.

About

About Percentage Difference Calculator

Compare two values using the symmetric midpoint formula. See the percentage difference, absolute difference, and percent change from A to B.

Features:

Calculate percentage difference between two values
See absolute difference
See percent change from A to B
Works with any numbers

FAQ

How do you compute percentage difference?

|A − B| ÷ ((|A| + |B|) ÷ 2) × 100%. For 80 and 100 that gives 22.22%.

How is that different from percent change?

Percent change uses a starting value: ((B − A) ÷ |A|) × 100%. From 80 to 100 it is +25%, and from 100 to 80 it is −20%.

What if a value is 0?

Percent change from 0 is undefined, and percentage difference is undefined only when both values are 0.

Do you round?

We show two decimal places for readability.

What Is a Percentage Difference Calculator?

A percentage difference calculator measures the relative difference between two values without treating either one as the original. It uses the average of both values as the reference, making the result symmetric — the percentage difference between A and B equals the difference between B and A. This distinguishes it from percentage change, which always uses the starting value as the base.

Use this when comparing two peer values — two store prices, two measurements, two test scores — rather than tracking how one value changed from another over time.

How to Use This Percentage Difference Calculator

Enter the first value (V1).
Enter the second value (V2).
The calculator applies: |V1 − V2| ÷ ((|V1| + |V2|) ÷ 2) × 100.
The percentage difference is never negative — it expresses magnitude, not direction. The percent change shown beside it keeps the sign.

Worked Example: Comparing Two Store Prices

Store A sells a laptop for $1,200. Store B sells the same model for $1,050.

Step	Calculation	Result
Absolute difference	\|$1,200 − $1,050\|	$150
Average of both values	($1,200 + $1,050) ÷ 2	$1,125
Percentage difference	$150 ÷ $1,125 × 100	13.33%

The prices differ by 13.33% — the same result whether you compare Store A to B or B to A. Using percentage change instead: from A to B it’s −12.5%; from B to A it’s +14.3%. The difference formula is the neutral choice.

Percentage Difference vs. Percentage Change vs. Percentage Error

Concept	Formula	Reference	When to Use
Percentage Difference	\|V1−V2\| ÷ avg × 100	Midpoint	Comparing peers (no before/after)
Percentage Change	(New−Old) ÷ Old × 100	Original value	Measuring change over time
Percentage Error	\|Approx−Exact\| ÷ Exact × 100	Exact value	Measuring accuracy of estimate

Why the Midpoint Formula Is Symmetric

The percentage difference formula uses the average (midpoint) of the two values as the denominator — the mathematically neutral choice that doesn’t privilege either value as the true reference. It’s the standard in scientific literature when two measurements are compared without a known ground truth.

In contrast, percentage change uses the starting value as denominator, introducing direction and asymmetry. The difference formula always yields one result regardless of which value you label V1 or V2.

Tips and Common Mistakes

Don’t confuse with percentage change: Percentage change is directional and uses the original value. Use it for before/after comparisons. Use percentage difference for peer comparisons.
Values near zero inflate results: If one value is close to zero, the average denominator is small and the percentage difference balloons. Consider whether the metric makes sense near zero.
Result is never negative: The absolute values remove sign. If you need direction, use percentage change instead.

Frequently Asked Questions About Percentage Difference

What is the percentage difference between 80 and 100?

|80−100| ÷ ((80+100)÷2) × 100 = 20 ÷ 90 × 100 = 22.22%. Note: percentage change from 80 to 100 is 25%, and from 100 to 80 is −20%.

Can percentage difference exceed 100%?

Yes. Values like 1 and 1,000 produce |999| ÷ 500.5 × 100 ≈ 199.6%. If one value is zero and the other is not, the result is 200%. It is undefined only when both values are zero.

Is percentage difference the same as percentage error?

No. Percentage error uses the known exact value as denominator. Use it when one value is the accepted truth; use percentage difference when neither value is privileged.

Related Calculators

Percentage Calculator — find %, percent of a number, change
Percentage Increase Calculator — directional percent change
Discount Calculator — percent off and sale price

Enter any two values to see the percentage difference between them, the absolute difference, and the percent change from the first value to the second. Percentage difference uses the midpoint formula, |A − B| ÷ ((|A| + |B|) ÷ 2) × 100, so it gives the same result whichever value you enter first. Results are displayed to two decimal places.

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