What is the difference between percent change and percent difference?

Percent change measures how a value has increased or decreased from a starting point, using the original value as the baseline. Percent difference compares two independent values symmetrically, using their average as the reference. Use percent change for before-and-after scenarios; use percent difference for peer comparisons.

When should I use percent change vs percent difference?

Use percent change when you have a clear starting point and want to measure growth or decline, such as price increases or salary raises. Use percent difference when comparing two independent measurements with no baseline, such as lab results or survey comparisons.

Is percent change the same as percent difference?

No, they are different. Percent change is directional and asymmetric, using the original value as the denominator. Percent difference is symmetric and uses the average of both values as the denominator. They produce different results and serve different purposes.

Percent Change vs Percent Difference (With Examples)

Many people confuse percent change and percent difference, but they answer different questions. Percent change measures how a value has shifted from a starting point, while percent difference compares two independent values. Understanding which one to use ensures accurate calculations and better decision-making. Use our percentage change calculator to instantly compute either metric, or read on to learn when to use each one.

What is percent change?

Percent change measures how much a value has increased or decreased from an original starting point. It's directional, meaning it shows whether the change is positive (increase) or negative (decrease). The original value serves as the baseline for comparison.

When it's used: Tracking salary increases, monitoring price changes, measuring sales growth, following weight loss progress, or comparing any before-and-after scenario. If you know the starting point and want to measure how much something has grown or shrunk, use percent change. This includes calculating percentage increases and decreases.

What is percent difference?

Percent difference measures the gap between two independent values without treating either as a baseline. It's symmetric, meaning the result is the same whether you compare A to B or B to A. Both values are treated equally, and their average serves as the reference point.

When it's used: Comparing lab measurements, evaluating test results from two groups, checking quality between two batches, or analyzing any situation where neither value is the "starting point." If you're comparing two measurements of equal importance with no clear baseline, use percent difference.

Key differences between percent change and percent difference

Percent Change

Direction: Shows increases or decreases
Baseline: Uses original value as denominator
Symmetry: Asymmetric (order matters)
Sign: Positive for growth, negative for decline
Use: Before-and-after scenarios

Percent Difference

Direction: Shows magnitude only, no sign
Baseline: Uses average of both values
Symmetry: Symmetric (order doesn't matter)
Sign: Always positive
Use: Independent value comparisons

Percent change vs percent difference: examples

Example 1: Before vs After Value (Price Change)

Scenario: A product was $50 and now costs $65. You want to know if the price increased.

Use percent change:

(65 − 50) ÷ 50 × 100 = +30% increase

This tells you the price rose by 30% from the original. The directional information (+) is valuable here because you're measuring change from a specific starting point.

Example 2: Comparing Two Independent Values (Lab Results)

Scenario: Two lab tests measured the same substance and got 40mg and 50mg. You want to know how different the measurements are.

Use percent difference:

|40 − 50| ÷ ((40 + 50) ÷ 2) × 100 = 18.18% difference

This tells you the measurements vary by 18.18%. Neither measurement is treated as "correct," just compared to their average. The results are symmetric: you'd get the same answer if you swapped the values.

When should you use percent change vs percent difference?

Choose percent change when:

You have a clear starting point and ending point
You want to measure growth or decline
You care about direction (positive/negative)
The original value is your reference
Examples: salary raises, stock prices, weight loss, profit margins

Choose percent difference when:

You're comparing two measurements without a baseline
Neither value is inherently the "original"
You want a symmetric comparison
You care about the magnitude of difference
Examples: lab results, survey comparisons, quality control, peer comparisons

Common mistakes people make

Using percent difference for before-and-after: If you have a starting point, percent change is more intuitive and meaningful. Percent difference obscures the directional information.
Using percent change for peer comparisons: When comparing two independent measurements with no clear baseline, percent change can be misleading because it treats one arbitrarily as the "original."
Confusing the formulas: Percent change uses the original value in the denominator; percent difference uses the average. This matters and changes the result significantly.
Ignoring symmetry: Percent change isn't symmetric (50→100 is +100%, but 100→50 is −50%), while percent difference is. Choose the method that matches your problem.

Percent Change vs Percent Difference