Transformation Efficiency Calculator

Calculate bacterial transformation efficiency in CFU/μg DNA to assess competent cell quality and optimize cloning protocols

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CFU/μg DNA
Total DNA Used--
DNA in Transformation--
DNA Plated--
Total Colonies Expected--

What is Transformation Efficiency?

Transformation efficiency measures the competence of bacterial cells to take up foreign DNA, expressed as colony forming units (CFU) per microgram of DNA. It's essential for assessing competent cell quality and optimizing transformation protocols in molecular cloning.

How to Use This Calculator

  1. Enter vector concentration and volume used
  2. Input ligation and transformation volumes
  3. Enter SOC recovery volume and volume plated
  4. Count and enter the number of colonies on your plate
  5. Calculate to get transformation efficiency in CFU/μg

Interpreting Results

Transformation efficiency benchmarks:

  • Excellent: >108 CFU/μg (Ultra-competent cells)
  • Good: 107 - 108 CFU/μg (High-efficiency cells)
  • Fair: 106 - 107 CFU/μg (Standard cells)
  • Poor: <106 CFU/μg (Needs optimization)

Example Calculation

Typical transformation parameters:

Vector: 10 ng/μl × 1 μl = 10 ng
Ligation: 10 μl total
Transform: 2 μl used
SOC: 1000 μl added
Plated: 100 μl
Colonies: 150

Result: 7.5 × 107 CFU/μg

Formula Explanation

The calculation accounts for all dilution steps:

DNA plated = (Conc × Vol) × (Transform/Ligation) × (Plate/SOC)

Efficiency = Colonies / DNA plated (μg)

The formula adjusts for the fraction of ligation used in transformation and the fraction of recovery culture plated.

FAQ

Q: Why is my transformation efficiency low?
A: Low efficiency can result from old competent cells, improper thawing, heat shock duration, or DNA quality issues.

Q: Should I plate different volumes?
A: Yes, plate 10-100 μl to get 50-300 colonies for accurate counting. Too few or too many colonies reduce accuracy.