Percentage Difference Calculator

How to use the percentage difference calculator

Enter any two numbers in the First Value and Second Value fields — order does not matter. The calculator shows the percentage difference between them, the raw absolute difference, and the average of the two values. All three results update instantly as you type. The result is always a positive percentage because percentage difference measures the size of the gap relative to the midpoint, not the direction of change. Use decimals freely: you can compare 2.718 and 3.141 as easily as whole numbers.

How the percentage difference calculator works

The formula is: Percentage Difference = (|Value1 − Value2| ÷ ((Value1 + Value2) ÷ 2)) × 100. Take the absolute difference between the two numbers, divide it by their average, and multiply by 100. For 80 and 100: |80 − 100| = 20; average = (80 + 100) ÷ 2 = 90; 20 ÷ 90 × 100 = 22.2%. The two values differ by 22.2% relative to their midpoint. Because both the absolute difference and the average are symmetric, swapping the two values always gives the same result.

When to use this calculator

Use percentage difference when comparing two values that have equal standing — neither is clearly the “before” or “reference” value. For example: comparing prices from two competing suppliers to see how far apart they are; comparing two scientific measurements where you want to quantify the discrepancy; analyzing the performance gap between two stores, two product categories, or two employees without implying one is the baseline; comparing survey results from two demographic groups; or checking how far two instruments or sensors read differently in quality control. When you have a clear original and new value (like a price change over time), use the percent change calculator instead.

Frequently asked questions