Cell Doubling Time Calculator
Calculate a culture's doubling time and number of doublings from start and end counts over a set time.
For a culture growing exponentially, the doubling time is how long it takes the population to double. From a start and end count over a known stretch of time, doubling time = time × ln2 ÷ ln(final ÷ initial). Go from 10,000 to 80,000 cells in 24 hours and each doubling takes 8 hours.
Doubling time
8hours
Number of doublings
3
How it works
When cells grow exponentially, the population multiplies by a fixed factor over equal stretches of time. The doubling time is how long it takes that population to double.
Enter the count you started with, the count you ended with, and how much time passed. The tool computes doubling time as time × ln2 ÷ ln(final ÷ initial), which is the exponential-growth formula rearranged.
It also reports the raw number of doublings, log2 of the fold change. Grow a culture eightfold and that's exactly three doublings, so a 24-hour run gives an 8-hour doubling time.
Frequently asked questions
What units does the doubling time come out in?
Whatever time unit you type in. Enter the elapsed time in hours and the doubling time is in hours; use minutes or days and the answer follows suit.
Why does the final count have to be bigger than the initial?
The formula describes growth. If the count stayed flat or fell, there's no doubling to measure, so the tool asks for a final count larger than the starting one.
Does this assume perfectly exponential growth?
Yes. It treats the culture as growing at a steady exponential rate over the whole interval. If cells enter a lag or plateau phase, the real doubling time varies across that window.