Cell Counting & Seeding Calculator

How the Grid Works

The haemocytometer grid is divided into nine 1 mm × 1 mm squares, each with a depth of 0.1 mm. This means each large square holds a volume of 1 mm³ = 0.1 µL. A dilute cell suspension is loaded under the coverslip, and cells are counted in one or more of these squares. The cell concentration is then calculated from the count, dilution factor, and grid geometry:

Counting Best Practices

• • Count cells in at least 4–5 squares to reduce sampling error
• • Use 50–200 cells per square for optimal counting statistics
• • Allow 1–2 minutes for cells to settle before counting
• • Count in a systematic pattern (e.g., diagonal corners + center)
• • Count the same squares on both sides of the chamber and average

Trypan Blue Viability

Trypan blue is a vital dye that cannot cross intact cell membranes. Live cells remain unstained and appear clear, while dead cells take up the dye and appear blue. When using trypan blue, the cell suspension is typically diluted 1:1 with dye, resulting in a 2× dilution factor. Count live and dead cells separately to assess viability percentage (live cells ÷ total cells × 100%).

Microfluidics & Single-Cell Encapsulation

In microfluidic droplet generation systems, the cell concentration determines the distribution of cells per droplet. The probability of encapsulating exactly one cell per droplet follows Poisson statistics: P(n) = (λⁿ × e⁻λ) ÷ n!, where λ is the average number of cells per droplet. To maximize single-cell encapsulation (λ ≈ 0.1), you need precise cell counting and controlled seeding.

Limitations

Haemocytometer counts are manual and subject to sampling variability. The method works best for cell suspensions with adequate cell size (typically 8–20 µm). For higher precision or automated counting, flow cytometry or automated cell counters are preferred. Always count in duplicate or triplicate and use the average.