# I. Population doubling time (PDT)

The population doubling time of a culture is calculated by the following equation:

PDT in hours = ln2 * (hours of culture) / ln(fold change in cell number)

(Note: PDT is an estimate of the cell cycle time of the dividing cells in a culture only when the dividing fraction of new cells approaches 100% and the cell death rate is insignificant.)

To Calculate PDT:

Enter:
• t1, time in hours when culture started (usually 0)
• t2, time in hours when culture period ended
• N1, number of cells in culture at time = t1
• N2, number of cells in culture at time = t2
 t1 t2 N1 N2

Result:

# II. Cell Population Doublings

The number of cell population doublings during a period of culture is calculated by the following equation:

Number of cell doublings = ln(fold increase in cell number)/ln2

To calculate Cell Population Doublings:

Enter:
• N1, Number of initial cells
• N2, Number of cells at the end of the period of culture
 N1 N2

Result:

# III. Cumulative Population Doublings (CPD)

A CPD data graph can be generating by calculating the number of cell doublings for a series of consecutive culture intervals and summing the values sequentially.

To generate CPD for a serially passaged culture enter the following data:

Initial Cell Number:

Passage Number Passage Interval Time in Hours Cell Number at End of Passage Interval Transferred Cell Number
1

Result:
Passage Number Hours of Culture CPD

Calculator V1