From reference to calculation
HeLa: turn a surface-density target into a dispensing plan
An adherent-cell reference describes the culture conditions. A seeding plan also needs your measured viable stock, the actual growth area and a defined endpoint.
Scientific contributor: Dr. Tayner Rodriguez Garzon · Published by Cell Culture Tools · How content is prepared
Keep the product and the experiment separate
The ATCC CCL-2 reference uses EMEM with 10% FBS at 37°C and 5% CO₂. That identifies the formulation represented by this profile. It does not select a seeding density for your particular imaging, treatment or endpoint assay.
For an area-based experiment, record the plate catalogue number and cells/cm² together. A count per well cannot be transferred unchanged between well formats: the same count on a smaller area creates a different initial surface density. A split ratio also cannot recover the missing count unless the viable yield of the source culture is known.
Worked example: one six-well plate
Assume a lab-selected target of 20,000 viable cells/cm², six wells of 9.6 cm² each, 2 mL final volume per well, and a stock already reported as 1,000,000 viable cells/mL. These are demonstration inputs, not a recommended HeLa assay protocol.
Each well needs 20,000 × 9.6 = 192,000 viable cells. Divide that count by the viable stock concentration to obtain the stock volume. The fresh-medium contribution is the chosen final volume minus that stock volume.
| Quantity | One well | Six wells |
|---|---|---|
| Viable cells | 192,000 | 1,152,000 |
| Stock contribution | 0.192 mL | 1.152 mL |
| Fresh complete medium | 1.808 mL | 10.848 mL |
| Final volume | 2 mL | 12 mL |
What changes when the count changes?
If 1,000,000 cells/mL is a total count at 80% viability, the viable stock is 800,000 cells/mL. The same cell target then requires 0.240 mL stock and 1.760 mL fresh medium per well. Keeping the original 0.192 mL stock addition would deliver only 153,600 viable cells, 20% below the intended count.
Enter 100% in the viability field when the stock concentration is already a live-cell concentration. Keep enough available stock for every intended well, then calculate any protocol-defined transfer allowance separately. The calculator checks this volume and cell budget; it cannot predict attachment or later confluence.
Sources and the next calculation
ATCC CCL-2: HeLa product information supports the stated product context. The interpretation above was prepared using product information retrieved on 1 November 2026; the reference cards retain their own field-review dates. The worked comparisons are original arithmetic examples, not reported experimental results.
The 9.6 cm² well area is from Thermo Fisher’s table for Nunc 140675. Check your actual plate.
Spot an unclear assumption? Send the page, input values and source for a correction.