Estimate viable cell concentration from an optical density reading.
Pick your organism or enter your own calibration factor — then confirm it with a real plate count.
What is the OD600 method?
OD600 measures how cloudy your liquid culture is by shining 600 nm light through it — the more cells present, the more light gets scattered and the higher the reading. It’s a fast way to estimate cell density, but since it also “sees” dead cells and debris, you calibrate it against an actual plate count (CFU) for true viable numbers.
OD is an estimate — a plate count is the truth. The conversion factor differs by strain, medium and instrument.
Plate a dilution, count the colonies with the AI Colony Counter, and calibrate your own OD-to-CFU factor in minutes.
Preset factors are widely cited approximations and depend heavily on organism, growth phase, cuvette path length and spectrophotometer. For quantitative work, always calibrate against your own viable plate counts.