Free · Laboratory calculations

Exponential Bacterial Growth & Doubling Time

Relate initial and final populations, elapsed time, hourly fractional growth and doubling time during ideal exponential growth.

Calculator inputs

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Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

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Starting with 100 cells and doubling each hour gives 400 cells after 2 hours. The hourly fractional increase is 1, meaning 100% per hour.

N(t) = N₀(1 + r)^t; doubling time = t ln(2) / ln[N(t)/N₀], with t in hours

Enter these known values and leave the other values blank.

This model describes positive exponential growth with a constant fractional increase per hour. Enter 0.1 for 10% hourly growth; the field is not a percentage selector.
Changing the elapsed-time unit does not change the rate basis: growth rate remains per hour. Population values may be estimates; fractional predictions are not literal fractional organisms.
Initial population and duration are positive, and final population exceeds initial population. Zero growth has no finite doubling time and is outside this tool’s finite-doubling domain.
Lag, nutrient limits, carrying capacity and death phases are not modeled. These equations do not validate cultivation conditions or predict a particular organism’s behavior.

No. It means a fractional hourly increase of 1, or 100%, so the population doubles each hour. One percent is 0.01.

Yes. The time selector converts minutes to hours before evaluating the model. Keep the fractional growth input on its hourly basis.

Bookify limits finite doubling calculations to positive exponential growth and a positive starting population.