1. What is Percent Difference?

Percent difference is a measure of how much two numbers differ relative to their average. It's commonly used to compare experimental values with theoretical values, or to measure change over time.

2. How the Calculation Works

The percent difference is calculated using:

Where:

• |New Value - Old Value| — Absolute difference between the two values
• (New Value + Old Value)/2 — Average of the two values

Key Features: The result is always positive (absolute value), symmetric (same result regardless of which value is "new" or "old"), and expressed as a percentage.

3. When to Use Percent Difference

Common Applications:

• Comparing experimental results to expected values
• Measuring change between two time periods
• Comparing two measurement methods
• Analyzing differences between similar items

4. Using the Calculator

Instructions:

1. Enter the old (original) value
2. Enter the new (comparison) value
3. Click "Calculate" to get the percent difference

Note: Both values must be numbers. If both values are zero, the result will be undefined.

5. Frequently Asked Questions (FAQ)

Q1: How is percent difference different from percent change?
A: Percent change compares to the original value only, while percent difference compares to the average of both values.

Q2: What does a 0% difference mean?
A: A 0% difference means the two values are identical.

Q3: Can percent difference be greater than 100%?
A: Yes, when one value is more than 3 times the other, the percent difference exceeds 100%.

Q4: How should I interpret a large percent difference?
A: A large percent difference indicates significant variation between the values, which may or may not be meaningful depending on context.

Q5: When shouldn't I use percent difference?
A: Avoid percent difference when dealing with values that can be zero or when directionality (increase vs decrease) is important.