Split Ratio Calculator
Work out how much harvested cell suspension and fresh medium go into each new vessel for a given split ratio when passaging adherent cells.
Formula
- the N in a 1:N split: one vessel is divided among N vessels of the same size
How it works
A 1:N split distributes the cells from one vessel across N vessels of the same size, so each receives 1/N of the harvest. Dividing the harvested volume by N gives the volume per new vessel, and fresh medium makes up the rest of the culture volume.
A higher ratio leaves each new vessel sparser and lengthens the time to the next passage.
Worked example
A flask is harvested into 10 mL and split 1:5 into flasks that each hold 12 mL.
- Suspension per flask = 10 mL / 5 = 2 mL.
- Fresh medium = 12 mL − 2 mL = 10 mL.
Add 2 mL of suspension and 10 mL of fresh medium to each of five flasks. Each receives 20% of the harvest.
These are the values the calculator opens with, so you can check its output against this example.
Assumptions
- The new vessels have the same growth area as the one harvested.
- The harvested suspension is well mixed.
Common mistakes
- Applying a ratio across vessels of different sizes. Moving from a T-25 to a T-75 already triples the area.
- Splitting by ratio when reproducibility matters. Counting and seeding at a fixed density is more consistent between passages.
- Splitting so sparsely that the cells stall. Many lines need a minimum density to grow.
Related tools
Related equipment
Service documentation, failure modes and parts for the instruments this calculation is used with.