Compare Two Values with Percentage Difference
Calculation
Quick Tips
- No Direction
Percentage difference doesn't care which value is older or newer. It just measures the gap between them.
- Always Positive
Because it uses the absolute value, the result will always be a positive percentage.
- Lab Reports
This calculation is extremely common in science and chemistry labs to compare experimental results against observed values.
- Symmetry
The difference between 80 and 100 is the same as the difference between 100 and 80 (22.2%).
How to Use This Tool
- 1
Enter your first number into the Value A field.
- 2
Enter your second number into the Value B field.
- 3
The calculator will measure the gap between them relative to their average.
The Mathematics
Percent Diff = |A - B| / ((A + B) / 2) × 100First, find the absolute difference between the two numbers. Then, find their average. Finally, divide the difference by the average and multiply by 100 to get the percentage difference.
Percentage Difference vs. Percentage Change
Percentage difference is used when comparing two values of the same type (like the scores of two different students) where neither is a baseline. Percentage change is for tracking a single value over time.
Frequently Asked Questions
Why is the percentage difference between 80 and 100 not 20%?
Because percentage difference divides the gap (20) by the *average* of the two numbers (90). 20 / 90 = 22.2%. If you want to know the change from an old value of 80 to a new value of 100, use the Percentage Change Calculator.
When should I use percentage difference?
Use it when comparing two values of the same type where neither one is obviously the "starting" or "correct" value, such as comparing the heights of two people, or the grades of two friends.
Why do science teachers ask for this?
In lab experiments, percentage difference is used to assess the precision of two repeated experimental measurements to see how closely they agree with each other.
Explore More Educational Tools
Unlock your academic potential with our suite of free premium calculators.