Cell culture plate knowledge base
Every question the culture guides answer, organized by topic, plus seeding density worked out in full and the edge well problem as culture sees it.
Culture plate questions repeat in a pattern: which format, which surface, how many cells, and why the edges look wrong. This page indexes the answers across this guide and the sister guides, and works two of them, seeding density and edge wells, in full below.
Start here
- What is a cell culture plate? The definition, and the formats with their jobs.
- The complete guide to cell culture plates: the five surface families.
- Treated vs untreated, and why cells fail to attach, on the homepage.
Formats and seeding
- Formats and growth areas: the area table and seeding numbers per format, including 384.
- Choosing by format inside the complete guide.
Surfaces
- Surfaces in full: treated against untreated, coatings, well shapes, and white plates for luminescence.
- Binding surfaces on the ELISA guide: the parallel problem in assay plates, protein instead of cells.
Seeding density, worked out
Seeding is area arithmetic. Decide the density the experiment wants on the surface, in cells per cm2, from the cell line and the confluency target at readout; multiply by the well growth area; that is the cells per well. Worked example, with the areas on the formats page: at a target of 20,000 cells per cm2, a 96 well (0.32 cm2) takes about 6,400 cells per well, a 24 well (1.9 cm2) about 38,000, and a 384 well (0.06 cm2) about 1,200. Two habits keep the arithmetic honest: seed from a single well-mixed suspension so wells differ by sampling, not by settling, and titrate once per line, because the density that reads as a tidy 70 percent confluent for one line is a carpet for another. Seeding numbers quoted per well without the area and the line are not transferable, which is why this site quotes areas and lets the multiplication travel.
Edge wells in culture
The edge effect has a culture-specific mechanism: over days in the incubator, perimeter wells lose water fastest, so their media concentrates, osmolarity climbs, and growth slows or morphology shifts while center wells look normal. It is the same physics as the assay edge effect, given days instead of minutes to work. The culture fixes: fill unused perimeter wells with sterile media or buffer so evaporation spends itself there; keep incubator humidity up and avoid fan-dried shelves; let the seeded plate rest briefly at room temperature so cells settle evenly before the incubator; and for long cultures, rotate plate position. Where the experiment allows it, design the layout so comparisons live in the interior and the perimeter is a moat, not data. The general treatment is in the microplates knowledge base.
Related guides
Common questions
Why are my edge wells growing slower than the center?
Evaporation. Perimeter wells lose water fastest over days of incubation, concentrating the media and raising osmolarity at the edges. Fill unused edge wells with sterile media or buffer, keep humidity high, and let seeded plates settle evenly before incubating.
How do I calculate how many cells to seed per well?
Multiply the growth area of the well by the density your experiment targets on the surface, in cells per cm2. A 96 well has about 0.32 cm2, so at 20,000 cells per cm2 the seeding is about 6,400 cells per well. Titrate once per cell line; densities do not transfer between lines unchanged.
Can I reuse a cell culture plate?
No. The treated surface degrades with washing and sterilization, and residues from a previous culture carry over. Culture plates are single use; the saving is small against an attachment problem or a contaminated line.
What is the growth area of a 24 well plate?
About 1.9 cm2 per well. The full ladder runs from about 9.5 cm2 (6 well) through 3.8 (12), 1.9 (24), 0.95 (48), and 0.32 (96), down to about 0.06 cm2 at 384; areas vary slightly by maker.