Percent Difference Calculator
Free percent difference calculator. Find the percentage difference between two values. Compare prices, measurements, and statistics with this easy-to-use tool.
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Understanding results
The calculator provides:
- Percent Difference: How far apart the two values are as a percentage of their average
- Absolute Difference: The numeric difference between the values
- Average: The mean of the two values
A lower percent difference means the values are more similar; a higher percent difference means they're more dissimilar.
Purpose
The percent difference calculator measures how far apart two values are, expressed as a percentage of their average. Unlike percentage change (which has a direction), percent difference is a symmetric measure—it gives the same result regardless of which value you enter first.
Percent difference is commonly used in science, statistics, and quality control to compare measurements, experimental results, or any two values without implying that one is the "original" or "reference" value.
How to use
Using the percent difference calculator:
- Enter the First Value: Input any number you want to compare.
- Enter the Second Value: Input the second number to compare.
- View Results: The calculator shows the percent difference between the two values.
Note: The order of values doesn't matter—you'll get the same result either way.
Examples
Example 1: Comparing Prices
Store A sells a product for $45, Store B for $52.
- Difference: |$45 - $52| = $7
- Average: ($45 + $52) / 2 = $48.50
- Percent Difference: ($7 / $48.50) × 100 = 14.43%
Example 2: Measurement Comparison
Two measurements of the same object: 15.2 cm and 15.8 cm.
- Difference: |15.2 - 15.8| = 0.6 cm
- Average: (15.2 + 15.8) / 2 = 15.5 cm
- Percent Difference: (0.6 / 15.5) × 100 = 3.87%
Example 3: Experimental Results
Two trial results: 250 and 275.
- Difference: |250 - 275| = 25
- Average: (250 + 275) / 2 = 262.5
- Percent Difference: (25 / 262.5) × 100 = 9.52%
How it works
Formula: Percent Difference = (|V1 - V2| / ((V1 + V2) / 2)) × 100
Step by step:
- Find the absolute difference: |Value1 - Value2|
- Calculate the average: (Value1 + Value2) / 2
- Divide and convert: (Difference / Average) × 100
Example: Values 80 and 100
- Difference: |80 - 100| = 20
- Average: (80 + 100) / 2 = 90
- Percent Difference: (20 / 90) × 100 = 22.22%
FAQ
What is the difference between percent change and percent difference?
Percent change measures change FROM one value TO another (has direction, can be positive or negative). Percent difference measures how far apart two values are relative to their average (symmetric, always positive, no direction implied).
When should I use percent difference vs percent change?
Use percent change when one value is clearly the 'before' and one is the 'after' (e.g., stock price over time). Use percent difference when comparing two values without a clear reference point (e.g., comparing two different measurements).
Does the order of values matter for percent difference?
No, percent difference is symmetric. Whether you enter 100 and 120 or 120 and 100, you get the same result because the formula uses absolute difference and average.
What is the percent difference between 50 and 75?
Difference: |50 - 75| = 25. Average: (50 + 75) / 2 = 62.5. Percent Difference: (25 / 62.5) × 100 = 40%.
Can percent difference be greater than 100%?
Yes, when the values are very different relative to their average. For example, comparing 10 and 100: Difference = 90, Average = 55, Percent Difference = 163.64%.
Methodology
The percent difference formula is:
Percent Difference = (|Value1 - Value2| / ((Value1 + Value2) / 2)) × 100
Or simplified:
Percent Difference = (|Difference| / Average) × 100
Where |...| means the absolute value (always positive).
Example Calculation
Compare 100 and 120:
- Absolute Difference = |100 - 120| = 20
- Average = (100 + 120) / 2 = 110
- Percent Difference = (20 / 110) × 100 = 18.18%
Validation & Accuracy
Tested: Verified against statistical calculators and scientific applications.
Accuracy: Results are exact, rounded to 2 decimal places.
Sources
Based on standard statistical formulas for percent difference, commonly used in scientific research, quality control, and data analysis.