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.

Counted concentration

A finite measured or assumed value greater than or equal to 0, expressed in cells/mL.

Dilution factor

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

The implementation follows this calculation rule: Recover the original cell concentration by scaling a counted dilution.^[1]

Original concentration

The calculated original concentration in cells/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. Ratios and percentages become unstable when their denominator is small, uncertain, or defined differently between samples.

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.

• Cell Dilution C1V1=C2V2

  Solve C1V1=C2V2 for the stock volume needed to reach a target concentration.

• Hemocytometer Cell Count

  Convert the average cells per hemocytometer square into cells per milliliter.

• CFU Per mL

  Estimate colony-forming units per milliliter from a plate colony count, dilution factor, and plating volume.