# Cell Doubling Time - (Mar/29/2010 )

Hi all,

I've been looking in the archives to get a method of accurately measuring cell doubling time and I found posts that pointed to this website: http://www.doubling-time.com/compute.php?lang=en

Seems very useful, however, when i plug in the following data for an experiment ........
0 500000
5 640000
24 1880000
29 3000000
48 4200000
53 4320000
77 11760000
96 16640000

...... it generates a graph giving an equation of ......... "amount=946090.4145*e0.0307*time"

My problem is that when I plug the same data into excel and generate the graph there with an exponential trendline, the equation comes out as ......... y = 664510e0.0362x

Using the "doubling time = ln(2)/growth rate" formula, this results in quite a different answer.

Can anyone explain the discrepancy to me? Does the website use a different trendline calculation?

Many thanks

-squallweathered-

ya... me too having the same problem understand the equation.
I have cells with my gene of interest and another one carries vector control.
From the cell count, it is very obvious that the cells with my gene of interest grow faster compare to vector control.
When I use the calculator, it gave me:
Cell with GOI: 32.93
Vector control: 29.7

Is the reading indicator of how fast it grows? It puzzles me too...

-sanjiun-

I've sent them an e-mail regarding this. Here is the reply:

Hi,

The equation used for several time points is based on least square methods. The equation minimized the distance between the points and the curve.

The units are the one you use for time. For example, if you use hours, then the results will be in hours.
In your case I guess the doubling time of the cells with the GOI is 32.93 hours. In other words, the cell number doubles every 32.93 hours.

If you want, send me your cell counts, I will check it.

Regards,

Vincent Roth MD

-sanjiun-

Thanks for sharing the info!

-squallweathered-