Hemocytometer Cell Count Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/9/2026
Cell concentration is calculated with (cells counted ÷ squares counted) × dilution factor × 10⁴. For 200 cells counted over 4 large squares, with a 1:2 dilution, the concentration is 1,000,000 cells/mL.
Explanation
The hemocytometer (commonly called a Neubauer chamber, or Malassez chamber depending on the model) is the reference tool for manually counting cells in suspension under a microscope, despite the widespread use of automated counters in many labs. Its etched grid marks out squares of precisely known volume: one large corner square corresponds to a volume of 0.1 mm³, or 10⁻⁴ mL. It's this geometric constant, specific to the instrument rather than the sample, that explains the 10⁴ factor in the formula: it converts a number of cells counted in a tiny volume into a concentration per milliliter, the unit usually used to express a cell culture's density. The dilution factor must also be accounted for when the sample was diluted before counting, generally with trypan blue, a dye that also distinguishes living cells from dead ones (only dead cells, with a damaged membrane, absorb the dye) — this calculator assumes only the relevant cells (living, or total depending on the protocol) were counted. To limit sampling error, it's recommended to count several large squares (generally the 4 corner squares) and use their average rather than a single square. To amplify a sequence of interest before culturing, see our PCR amplification calculator; to assess a growth rate from several successive counts, our population growth rate calculator.
Example: 200 cells counted over 4 large squares, 1:2 dilution
Inputs
Cells counted: 200. Squares counted: 4. Dilution: ×2.
Calculation
Average per square = 200 ÷ 4 = 50 cells. Concentration = 50 × 2 × 10⁴ = 1,000,000 cells/mL.
Result
This culture's concentration is about 1,000,000 (1 × 10⁶) cells per mL.
Frequently asked questions
Why count several squares rather than just one?
Because the distribution of cells in the chamber is never perfectly uniform: counting a single square exposes you to significant sampling error, especially if few cells are present there. Counting the 4 large corner squares and using their average (as this calculator does via the total cell count divided by the number of squares) noticeably reduces this variability.
What should you do if the cell count varies a lot from one square to another?
A large gap between squares (generally beyond 10-20% variation around the average) signals an uneven distribution of cells in the chamber, often due to poor mixing of the sample before loading or an air bubble. In that case, it's recommended to reload the chamber after carefully remixing the sample rather than trusting an unreliable count.
Does this calculation give only living cells?
That depends entirely on what was counted under the microscope, not on the formula itself. With trypan blue staining, dead cells appear blue (dye absorbed) while living cells stay clear (intact membrane): you therefore need to decide, before counting, whether you want the number of living cells, total cells, or to calculate a viability percentage separately.