Use this calculation for cell-culture or microscopy observations collected with one counting rule, assay gate, calibration, and unit convention. It is suited to documenting dilution, growth, labeling, geometry, or population fractions.

Colony count

An integer count greater than or equal to 0.

Dilution factor

A finite measured or assumed value greater than or equal to 1.

Plating volume

A finite measured or assumed value, expressed in mL.

The implementation follows this calculation rule: Estimate colony-forming units per milliliter from a plate colony count, dilution factor, and plating volume.^[1]

CFU per mL

The calculated cfu per ml.

Counts and fluorescence measurements can be biased by clumping, debris, segmentation, gating, background signal, saturation, sampling fields, or unequal viability. A calculated percentage does not identify the biological mechanism behind a change. The output is explicitly an estimate or proxy; preserve that label when reporting it.

Retain representative images or cytometry plots and include biological replicates. Orthogonal viability, proliferation, apoptosis, or direct counting assays can distinguish effects that a single cell metric conflates.

• CFU Total Estimate

  Estimate the total colony-forming units in a culture from concentration and volume.

• CFSE Dilution Factor

  Estimate cell division count from CFSE fluorescence dilution using the base two logarithm of the initial over current intensity.

• OD600 To CFU

  Convert an OD600 absorbance reading to an estimated bacterial density: CFU/mL = OD600 x conversionFactor, using a species-dependent factor that defaults to 1e9 CFU per OD600 unit.