Doubling times always depend on the cell line and on the culture conditions; check out the detailed information provided by the suppliers.

How to calculate the PTD you may find, for example, here:

https://asymmetrex.com/stem-cell-counting-center/

MCF-7 about 50 hours (range 30-72 hours)

https://www.dsmz.de/collection/catalogue/details/culture/ACC-115

https://www.atcc.org/products/htb-22

MDA-MB-231 about 25-30 hours

https://www.dsmz.de/collection/catalogue/details/culture/ACC-732

https://www.atcc.org/products/crm-htb-26

Hello Student F.

Population growth rates are a core property of cell lines with each cell line showing different cell proliferation kinetics during the log phase, and it is therefore the optimal phase for determining the population doubling time (PDT).

The doubling time can be estimated from the population size at two points. For cells growing exponentially, this value is well-defined. However, the more a cell culture strays from exponential growth, the more inaccurate the PDT becomes as a measure of population cell growth. Exponential growth is a consequence of growth laws in individual cells causing regular division. The addition of factors like cooperation or competition for resources creates a non-exponential population growth.

Also, the population growth rates can be influenced by many other factors like in controlled experiments, how quickly the population size changes over time, may correlate with the presence of drugs or toxins, or temperature, particular genetic changes in the cells, availability of nutrients for growth, etc.

You may calculate cell doubling time as below using growth rate.

N(t) = N(0) e^grt

gr= ln {N(t)/N(0)}/t

doubling time (t) = ln (2)/gr

where

N(t) is the number of cells at time t

N(0) is the number of cells at time 0

t is time (in hours)

gr is the growth rate

MCF-7 cells are generally a slow-growing population. It has a doubling time of 30-40 hours. MDA-MB-231 has a doubling time of 25-30 hours.

You may want to refer to the article attached below for more information.

Article Inferring time-dependent population growth rates in cell cul...

Best.

Seeding 100.000 cells to 6 well plate then count amount of cells after few days. For example on 1st day seeded 100.000 cells then in 5th days you get 600.000 , then go to doubling-time.com.. input your cells counting data... you can count the PDT directly