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Population Doubling Level Calculator

Calculate the population doublings in a passage from the cells seeded and harvested, and add them to a running cumulative population doubling level (PDL).

Formula

PD=log⁡2NharvestedNseeded\mathrm{PD} = \log_2\dfrac{N_{\text{harvested}}}{N_{\text{seeded}}}
PD=3.322 log⁡10NharvestedNseeded\mathrm{PD} = 3.322\,\log_{10}\dfrac{N_{\text{harvested}}}{N_{\text{seeded}}}
PDLcum=PDLprev+PD\mathrm{PDL}_{\text{cum}} = \mathrm{PDL}_{\text{prev}} + \mathrm{PD}
PD\mathrm{PD}
population doublings during this passage
PDL\mathrm{PDL}
total doublings since the culture was started

How it works

Passage number records how many times a culture has been split, but not how much it has grown, since that depends on the split ratio. Population doublings record the growth itself. Summing them across passages gives the population doubling level, the standard measure of the replicative age of a finite cell line.

The factor 3.322 is 1 / log₁₀(2), which converts a base-10 logarithm into doublings.

Worked example

5 × 10⁵ cells are seeded and 4 × 10⁶ are harvested. The culture was at PDL 21.5 before this passage.

  1. Fold expansion = 4 × 10⁶ / 5 × 10⁵ = 8.
  2. PD = log₂(8) = 3.00.
  3. Cumulative PDL = 21.5 + 3.00 = 24.50.

The passage added 3.00 population doublings, bringing the culture to PDL 24.50.

These are the values the calculator opens with, so you can check its output against this example.

Assumptions

  • Every seeded cell attached and divided. Low plating efficiency makes the true number of doublings higher.
  • Counts at seeding and harvest are viable cell counts.

Common mistakes

  • Using passage number as if it were PDL. Two labs at the same passage can be many doublings apart.
  • Losing track of the running total when a culture is frozen. Record the PDL on the vial.
  • Counting all harvested cells rather than viable ones.

Related tools

Cell Doubling Time CalculatorDoubling time from two cell countsOpen calculatorSplit Ratio CalculatorSuspension and medium per vessel when passagingOpen calculatorHemocytometer Cell Counting CalculatorCells per mL from a hemocytometer countOpen calculatorBacterial Growth Rate CalculatorSpecific growth rate and doubling timeOpen calculator

Related equipment

Service documentation, failure modes and parts for the instruments this calculation is used with.