Cell Doubling Time Calculator

Calculate how long it takes for a cell population to double, based on initial count, final count, and elapsed time.

Initial Cell Count (N₀)

Final Cell Count (Nt)

Elapsed Time (t)

Number of doublings:
n = log₂(N_t / N₀)

Doubling time:
T_d = t / n = t / log₂(N_t / N₀)

Equivalent form using natural log:
T_d = (t × ln 2) / ln(N_t / N₀)

Growth rate constant:
k = ln(2) / T_d (units: per hour)

Where N₀ = initial cell count, N_t = final cell count, t = elapsed time.

Assumes exponential (log-phase) growth throughout the entire elapsed time period.
Cell death, lag phase, and stationary phase are not accounted for; results are most accurate during active proliferation.
Both cell counts must be measured under identical conditions (same volume, same counting method).
Typical mammalian cell doubling times range from ~12 hours (HeLa) to ~24–48 hours for primary cells.
Formula source: Freshney, R.I. Culture of Animal Cells, 6th ed. Wiley-Blackwell, 2010.
Growth rate constant k is equivalent to the specific growth rate (μ) used in microbiology.

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