1. What is Dilution Factor?

The dilution factor (DF) is a ratio describing how much a sample has been diluted. It represents the factor by which the original concentration is reduced in each dilution step.

2. How to Calculate Total Dilution Factor

The total dilution factor is calculated by multiplying all individual dilution factors:

Where:

• \( DF_{total} \) — Total dilution factor (unitless)
• \( DF_i \) — Individual dilution factor at each step (unitless)
• \( n \) — Number of dilution steps

Example: For serial dilutions of 1:10, 1:100, and 1:1000, the total DF = 10 × 100 × 1000 = 1,000,000.

3. Importance in Microbiology

Details: Dilution factors are crucial for determining microbial concentrations, preparing samples within detection limits, and ensuring accurate colony counts in plating techniques.

4. Using the Calculator

Tips: Enter the number of dilution steps, then input each step's dilution factor. The calculator will compute the cumulative dilution factor.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between dilution factor and dilution ratio?
A: Dilution factor is the inverse of dilution ratio (e.g., 1:10 ratio = DF of 10).

Q2: How do I calculate CFU/mL from colony counts?
A: CFU/mL = (colony count) × (total dilution factor) / (volume plated in mL).

Q3: What are common dilution factors used in microbiology?
A: Common DFs include 10, 100, 1000, or serial decimal dilutions (e.g., 1:10 at each step).

Q4: How does this relate to serial dilutions?
A: Serial dilutions involve multiple sequential dilution steps where each step's output becomes the next step's input.

Q5: When would I need to calculate total dilution factor?
A: Essential for determining original concentrations in microbial enumeration, viral titrations, and various microbiological assays.