1. What is Fold Change?

Fold Change (FC) is a measure describing how much a quantity changes between two measurements. It is calculated as the ratio of the final value to the initial value, providing a unitless measure of relative change.

2. How Does the Calculator Work?

The calculator uses the Fold Change formula:

Where:

• \( Value1 \) — Initial value (unitless)
• \( Value2 \) — Final value (unitless)

Explanation: The formula calculates the relative change between two values, where a FC > 1 indicates an increase, FC < 1 indicates a decrease, and FC = 1 indicates no change.

3. Importance of Fold Change Calculation

Details: Fold change is widely used in biological sciences, particularly in genomics and proteomics, to quantify changes in gene expression, protein levels, and other molecular measurements between experimental conditions.

4. Using the Calculator

Tips: Enter both Value1 and Value2 as positive numbers. All values must be valid (greater than 0).

5. Frequently Asked Questions (FAQ)

Q1: What does a fold change of 2 mean?
A: A fold change of 2 means the final value is twice the initial value, indicating a 100% increase.

Q2: What does a fold change of 0.5 mean?
A: A fold change of 0.5 means the final value is half the initial value, indicating a 50% decrease.

Q3: Can fold change be negative?
A: No, fold change is always positive as it's a ratio of two positive values. For decreases, the value is between 0 and 1.

Q4: How is fold change different from percentage change?
A: Fold change is a multiplicative factor (Value2/Value1), while percentage change is (Value2-Value1)/Value1 × 100%. Fold change of 2 equals 100% increase.

Q5: When should I use fold change vs log2 fold change?
A: Fold change is used for direct comparison, while log2 fold change is often used in statistical analyses as it provides symmetric scaling around no change (0).