CFU Calculator

Calculate Colony Forming Units per mL from bacterial culture plate counts and dilution factors with statistical validation

Plate Data Entry
Sample Information

CFU Analysis Results

Individual Plate Results

PlateColony CountDilution FactorVolume (µL)CFU/mLLog10 CFU/mLStatus

What is CFU Calculator?

A Colony Forming Units (CFU) calculator is an essential microbiology tool that determines the concentration of viable bacterial cells in a culture. It calculates CFU/mL from colony counts on agar plates, accounting for dilution factors and plated volumes to provide accurate bacterial concentration measurements.

How to Use This CFU Calculator

Calculate bacterial concentration in three simple steps:

  1. Enter colony counts, dilution factors, and volumes for each plate
  2. Add multiple plates for statistical analysis
  3. View CFU/mL results with confidence intervals and validation

When to Use

This CFU calculator is essential for:

  • Bacterial culture viability assessment
  • Serial dilution analysis and validation
  • Quality control in microbiology labs
  • Growth curve experiments
  • Antibiotic sensitivity testing

Example Input

Sample bacterial culture data:

Plate 1: 156 colonies, 10^-5 dilution, 100 µL
Plate 2: 142 colonies, 10^-5 dilution, 100 µL
Plate 3: 38 colonies, 10^-6 dilution, 100 µL

Try with your own plate counts or use the Example button.

Example Output

CFU analysis results include:

Average CFU/mL: 1.45 × 10^8
Log10 CFU/mL: 8.16
95% CI: 1.32 × 10^8 - 1.58 × 10^8
Valid plates: 3/3

Results include statistical validation and confidence intervals.

FAQ

Q: What is the optimal colony count range?
A: 30-300 colonies per plate for accurate counting and statistical validity.

Q: How are confidence intervals calculated?
A: Using t-distribution for small samples or normal distribution for large samples (n≥30).

Q: What dilution factors should I use?
A: Start with 10^-3 to 10^-7 for most bacterial cultures, adjust based on expected density.