1. What is the CFU/ml Formula?

The CFU/ml (Colony Forming Units per milliliter) formula calculates the concentration of viable microorganisms in a sample. It's a fundamental calculation in microbiology used to quantify bacterial or fungal growth in liquid cultures.

2. How Does the Calculator Work?

The calculator uses the CFU/ml formula:

Where:

• \( C \) — Colonies counted (unitless)
• \( DF \) — Dilution factor (unitless)
• \( V \) — Volume plated (ml)

Explanation: The formula accounts for both the dilution of the original sample and the volume used for plating to determine the original concentration of microorganisms.

3. Importance of CFU/ml Calculation

Details: Accurate CFU/ml calculation is crucial for determining microbial concentrations in various applications including water testing, food safety, pharmaceutical quality control, and clinical microbiology.

4. Using the Calculator

Tips: Enter the number of colonies counted, the dilution factor used, and the volume plated. All values must be valid positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is an appropriate colony count range?
A: For accurate counting, colonies should be between 30-300 per plate. Counts outside this range may be less reliable.

Q2: How do I determine the dilution factor?
A: The dilution factor is the reciprocal of the dilution. For example, a 1:10 dilution has a dilution factor of 10.

Q3: Why is the volume plated important?
A: The volume plated determines what fraction of the diluted sample was actually used for colony formation and counting.

Q4: What are typical CFU/ml values?
A: Values can range from less than 10 CFU/ml in purified water to millions of CFU/ml in bacterial cultures, depending on the sample type.

Q5: Are there limitations to this calculation?
A: This calculation assumes that each colony arises from a single viable microorganism and that the plating was done with proper technique and appropriate dilutions.