Calculate fold change, the number of doublings, and doubling time from two cell counts and the elapsed time between them.
| Fold change | – |
| Doublings | – |
| Doubling time | – |
Use this calculator to estimate how quickly a cell culture or microbial population is growing when you have counts at two time points. The calculation assumes exponential growth over the measured interval, with no lag, death, or nutrient limitation.
Fold change is the final count divided by the initial count. The number of doublings is log₂ of that fold change. Doubling time is elapsed time × ln(2) ÷ ln(fold change), which is the same as elapsed time divided by the number of doublings. Use the same time unit for the elapsed-time input and the doubling-time result, for example hours or days.
The final count must be greater than the initial count, and both counts and the elapsed time must be positive.
Initial count: The cell count or cell density at the start of the interval. Use any consistent unit, such as cells/mL or CFU.
Final count: The cell count or cell density at the end of the interval. It must be higher than the initial count and expressed in the same unit.
Elapsed time: The time between the two measurements, in the unit you want for the doubling time (hours, days, or another unit).
Fold change: How many times the population increased (final ÷ initial).
Doublings: How many times the population doubled during the interval.
Doubling time: The time required for the population to double, in the same unit as the elapsed time.
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