Knockdown slows cell proliferation
Compare proliferation across a control and knockdown.
2 conditions · 3 wells · 0–96 h
Cell Doubling Time Calculator
FigranGet doubling time from cell counts or OD readings, with a 95% CI and a growth curve to download.
- Finds the exponential phase
- Replicates and 95% CI
- Growth curve as SVG or 300 DPI PNG
Data
Hollow points are outside the fitted window.
| Condition | Window | Td | 95% CI | μ / R² |
|---|---|---|---|---|
| Control | 24–72 hPoints used: 9 | 22.9 hReplicate mean ± SD: 23.0 ± 0.2 | 21.9–24.1 | 0.0302 /hR² = 0.997 |
| siRNA | 24–72 hPoints used: 9 | 31.4 hReplicate mean ± SD: 31.5 ± 0.4 | 29.8–33.3 | 0.0220 /hR² = 0.996 |
All-points comparison
Control: Using all points gives 26.6 h.
siRNA: Using all points gives 35.6 h.
Doubling times were estimated by least-squares linear regression of natural-log measurements on time over the exponential phase (Td = ln 2 / μ). The exponential phase was selected automatically. Each condition used 24–72 h, 3 time points and 9 observations. Each condition had 3 replicate wells. Slope confidence intervals were transformed to 95% doubling-time intervals when estimable.
Doubling time examples
Explore examples, then load one to use its data.
Drug treatment at three doses
Compare growth under three treatment conditions.
3 doses · 3 wells · 0–120 h
Doubling time from two counts at passage
Calculate growth between seeding and harvest.
Seeded 5×10⁵ · harvested 2.1×10⁶ · 72 h
Cumulative population doublings of MSCs
Track population doublings over successive passages.
8 passages · 44 days
Bacterial growth curve (OD600)
Subtract a medium blank before fitting E. coli growth.
OD600 every 30 min · 3 wells · blank 0.045
Yeast wild type versus mutant
Compare the growth of two yeast strains.
2 strains · 2 cultures · 0–12 h
How to calculate doubling time
Turn time-course measurements into a growth curve and a doubling time.
1Enter data
Paste time and one column for each replicate well.
2Check window
Review the selected window or choose your own.
3View results
Compare doubling time, confidence intervals and growth rates.
4Download
Download your figure and copy the methods text.
Doubling time formula
Doubling time (Td) can be estimated from two counts or from the specific growth rate (μ) during exponential growth.
How doubling time is calculated
Use two counts for a simple estimate, or fit the growth rate across an exponential interval.
Two counts
Δt is elapsed time; N₀ and N are the initial and final counts. The final count must exceed the initial count.
Log-linear regression
μ is the slope from fitting ln(count) against time during the exponential phase. A positive slope gives a doubling time in the input time unit.
Three methods for the same data
The default Control data give different estimates depending on which measurements are used.
| Method and measurements | Doubling time |
|---|---|
| First and last countsUses the mean counts at the first and last time points only. | 27.8 h |
| All time pointsFits all measurements across the complete time course. | 26.6 h |
| Exponential phaseFits only measurements in the selected 24–72 h interval. | 22.9 h |
During exponential growth, the log of cell count is approximately linear in time. Lag or plateau measurements can change the fitted slope, so selecting the exponential interval often gives a more relevant estimate.
How the confidence interval is calculated
The fit uses residual variation and a t distribution to estimate a 95% interval for the growth rate. Its bounds are then transformed into doubling time.
95% confidence interval
The lower and upper bounds are for μ. Both must be positive for the calculator to report a finite doubling-time interval.
Population doubling time and PDL
Use population doubling level (PDL) to track cumulative growth across successive cell passages.
Population doublings
The subscripts mark harvested and seeded cell counts for one passage.
Cumulative PDL
The starting PDL is the level before the first passage; add the population doublings (PD) from each passage.
Getting a reliable doubling time
Plan your measurements and report the conditions behind each estimate.
Enough time points
Measure at least three time points in the exponential phase.
Replicate wells
Use replicate wells and report per-well mean ± SD or the pooled 95% CI.
Blank-subtract OD readings
Subtract the medium blank from OD600 and stay in the linear range.
Bacterial example
28.2 min blank subtracted43.8 min no subtraction
Report the conditions
Report the temperature, medium, seeding density and fitted time window. This context helps others interpret and reproduce the result.
Doubling time FAQ
What is doubling time?
Doubling time is the time a population takes to double in number during exponential growth.
Why does the calculator use only part of my growth curve?
Lag and plateau phases can slow growth. Auto selects a fast, continuous log (exponential) phase; hollow points lie outside it, and you can change the window manually.
What is the difference between doubling time and generation time?
For bacteria dividing by binary fission, the terms are often equivalent: generation time g = t / n, where n = log₂(N/N₀). Population doubling time is not necessarily the cell-cycle length of every cell.
What is specific growth rate?
Specific growth rate (μ) is the slope of log population size against time; μ = ln 2 / Td. The doubling rate k = 1 / Td is expressed in doublings per unit time.
What is population doubling level (PDL)?
Population doubling level (PDL) is the accumulated number of population doublings across passages; each passage contributes log₂(cells harvested / cells seeded).
Can I use OD600 or confluence instead of cell counts?
Yes, when the measurement is proportional to cell number. Subtract the medium blank and check the instrument’s linear range; high confluence can cease to be proportional.
How should I report doubling time with replicates?
Report per-well mean ± SD or the pooled estimate with its 95% confidence interval, together with the fitted window and method. The results CSV includes each fitted well’s doubling time.
What is the doubling time of HeLa, HEK293 and E. coli?
It depends on the culture conditions, so measure it for your own medium, temperature and seeding density.
Is my data uploaded, and what can I download?
Calculations stay in your browser. Download SVG, 300 DPI PNG or CSV, and copy the methods text.
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Use your own counts or OD readings to create a growth curve.
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