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Transformation Efficiency Calculator

Measure how well your competent E. coli (or other) cells take up plasmid DNA. Use it after a control transformation, such as pUC19, to check a new batch of homemade or commercial competent cells.

Enter your colony count, how much DNA you transformed and how much of the recovery culture you plated. We'll work out your competent cells' efficiency in colonies per microgram of DNA.

The number of colonies on the plate you counted.

colonies

The amount of plasmid added to the competent cells, e.g. 100 pg.

Cells plus recovery medium, e.g. 50 µL cells + 950 µL SOC = 1000.

µL

How much you spread on the plate.

µL

Leave at 1 if you didn't dilute. For a 1:10 dilution, enter 10.

Enter your values and press Calculate to see your transformation efficiency.

How it's calculated

DNA plated (µg) = DNA used (µg) × (volume plated ÷ total recovery volume) ÷ dilution factor

Efficiency (CFU/µg) = colonies ÷ DNA plated (µg)

Count a plate with roughly 30–300 colonies for a reliable result. Chemically competent cells typically reach 10⁶–10⁹ CFU/µg; electrocompetent cells can exceed 10¹⁰ CFU/µg.