Bacterial Growth Calculator (Doubling Time and Generations)
Project how a culture grows, or find its doubling time from two counts.
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Bacterial Growth Calculator (Doubling Time and Generations) by TheCalcTools
How the Bacterial Growth Calculator (Doubling Time and Generations) works
During exponential (log) phase, every cell divides once per generation, so the population doubles each doubling time: N = N₀ × 2^(t/g).
From two counts, the number of generations is log₂(N/N₀) and the doubling time is the elapsed time divided by that. Real cultures slow down as nutrients run out (stationary phase).
The formula
Worked example
Using the default values shown in the calculator:
| Find | Final population from doubling time |
|---|---|
| Starting count (cells or CFU/mL) | 1000 |
| Time elapsed | 4 hours |
| Doubling time | 20 minutes |
| Final count | 4.096e+06 |
- 4 hours at a 20-minute doubling time is 12 generations.
- 1,000 × 2^12 = 4096000 cells.
Result:
| Final population | 4096000 |
|---|---|
| Generations | 12.00 |
| Doubling time (minutes) | 20.00 |
| Growth rate constant (per hour) | 2.0794 |
Frequently asked questions
What is the doubling time of E. coli?
About 20 minutes in rich medium at 37 °C, longer in poorer media or at lower temperatures.
Sources and further reading
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