Enter the number of colonies, dilution factor (the reciprocal of the dilution), and volume plated into the calculator to determine the bacterial concentration.
- All Biology Calculators
- Transformation Efficiency Calculator
- Specific Activity Calculator
- Cell Density Calculator
Bacterial Concentration Formula
The following formula is used to calculate a bacterial concentration.
BC = \frac{C \cdot DF}{V}- Where BC is the bacterial concentration (CFU/mL)
- C is the number of colonies counted on the plate
- DF is the dilution factor (reciprocal of the dilution; e.g., 1:2 dilution → DF = 2)
- V is the volume plated (mL)
To calculate a bacterial concentration, multiply the number of colonies by the dilution factor, then divide by the volume plated.
What is a bacterial concentration?
A bacterial concentration is a measure of the total number of bacteria per unit of weight or volume. This is typically measured in colony-forming units per milliliter of culture.
How to calculate bacterial concentration?
The following example problem outlines the steps needed to calculate a bacterial concentration.
First, determine the number of colonies. In this example, the number of colonies is 50.
Next, determine the dilution factor. This solution is a 1:2 dilution, so the dilution factor is 2.
Next, determine the volume plated. In this case, the volume plated is 0.1 mL.
Finally, calculate the bacterial concentration using the formula above:
BC = C * DF / V
BC = 50 * 2 / 0.1
BC = 1000 CFU/mL
