⏱️ Generation Time Calculator
Estimate the time required for a microbial population to double during exponential growth.
How to Use This Calculator
Measure culture densities
Record viable cell counts (CFU/mL) or optical density at the start and end of the exponential growth window.
Enter elapsed time
Provide the total incubation time between measurements in hours (or fractions of an hour).
Review growth metrics
Run the calculation to obtain total generations, average generation time, and specific growth rate.
Formula
n = log₂(Nt ÷ N0)
Generation Time (g) = t ÷ n
The specific growth rate (μ) is given by μ = n ÷ t. These relationships assume exponential growth without nutrient limitations between the two sampling points.
Full Description
Generation time (doubling time) captures how rapidly a microbial population divides under a specific set of conditions. By comparing population measurements taken during the exponential phase, you can quantify growth kinetics and evaluate how medium composition, temperature, or antibiotics impact cell proliferation.
While viable counts and OD readings are common proxies for cell number, ensure measurements fall within the linear detection range to avoid skewed calculations. Triplicate measurements further improve the reliability of estimated generation times.
Frequently Asked Questions
What units should I use for cell counts?
Use the same units (CFU/mL, cells/mL, OD units) for both initial and final measurements. The ratio drives the generation calculation, so consistent units are essential.
Can I calculate generation time from OD readings?
Yes. As long as OD values remain within the spectrophotometer’s linear range, the ratios approximate changes in cell number and yield reliable generation time estimates.
What if my culture is not in exponential phase?
The formulas assume exponential growth. Measurements during lag or stationary phases will distort the calculation. Select an interval where growth appears linear on a semi-log plot.
How can I improve accuracy?
Take replicate measurements, use fresh dilutions for viable counts, and ensure precise timing. Consistent incubator conditions and gentle mixing reduce variability between samples.