CFU calculator
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TOOL INDEX / 03 AVAILABLE

Microbiology calculators

Three calculators for everyday microbiology work. Each one computes from the values you enter, shows the formula behind the result, and states its assumptions. All calculations run locally in your browser.

01VIABLE COUNT

CFU/mL and CFU/g calculator

Calculate concentration from colony counts, dilution fraction, and plated volume — for liquid samples and homogenized solids.

Open calculator
02CELL DENSITY

OD600 cell density calculator

Estimate cells per mL from optical density using a conversion factor, linear curve, or logarithmic calibration you provide.

Open calculator
03DILUTION PLANNING

Serial dilution planner

Work out transfer and diluent volumes for each tube and follow the cumulative dilution factor through the series.

Plan dilution

What each calculator needs

CFU calculator
Colonies counted, the dilution of the tube plated (exponent, fraction, or factor), and the plated volume. Solid samples add sample mass and homogenization volume.
OD600 calculator
A measured OD600 and its blank, plus a calibration — a conversion factor, a linear curve, or a log model — built for your organism and instrument.
Serial dilution planner
The dilution per step (1:10, 1:2, or custom), the number of tubes, and the final volume per tube. Mixed step factors are supported.

Guides and methods

New to a calculation? The guides section walks through CFU counting, OD600 calibration, and dilution planning with worked examples. The calculation methods page collects every formula the tools use, with terms and limitations defined.