About this tool
The Cell Doubling / Generation Time Calculator is a free, in-browser tool for exponential microbial growth. From an initial count N₀, a final count N, and the elapsed time, it works out how long a population takes to double (the generation time), how many generations occurred, and the specific growth rate μ — or, in reverse, it projects the final count from a known doubling time. Everything is computed locally in your browser and nothing you enter is uploaded.
The method uses base-2 growth. The number of doublings is n = log₂(N/N₀), the doubling (generation) time is DT = t/n = t·ln2 ÷ ln(N/N₀), and the specific growth rate is μ = ln(N/N₀) ÷ t, which is related to doubling time by DT = ln2/μ. In the final-count mode the population grows as N = N₀·2^(t/DT).
Enter the elapsed time in whatever unit you like (minutes, hours, days) — the doubling time comes out in that same unit and the growth rate μ is per that unit. For a meaningful doubling time the culture must be growing, so the final count has to exceed the initial count; the tool flags the case where it does not.