Transformation Efficiency Calculator

How to calculate transformation efficiency

1. Type the colonies counted on the plate and the ng of DNA used in the transformation.
2. Type the volume after adding recovery medium and the volume spread on the plate, plus any dilution made before plating.
3. The efficiency appears in colony-forming units (cfu) per µg of DNA, with the ng of DNA that ended up on the plate.

Frequently asked questions

What is the formula?

Efficiency = colonies ÷ µg of DNA plated, where µg plated = µg transformed × volume plated ÷ total volume ÷ dilution.

What is a good efficiency?

Home-made chemically competent E. coli usually give 10⁶ to 10⁷ cfu/µg; commercial high-efficiency and electrocompetent cells give 10⁸ to 10¹⁰ cfu/µg. Counts between 30 and 300 colonies per plate give the most reliable figure.