Hemocytometer Cell Count

A hemocytometer lets you estimate how many cells are in a liquid by counting the cells in a known tiny volume and scaling that count up to 1 mL. The average number of cells per square is multiplied by the dilution factor because the sample is often diluted before counting, then multiplied by 10^4 because each large counting square corresponds to 10^-4 mL in the standard chamber depth. This turns a small-area count into a concentration in cells per milliliter.

Use this when counting cells manually under a microscope with a hemocytometer, such as yeast, cultured mammalian cells, algae, or blood cells after appropriate preparation. It is especially useful when an automated cell counter is unavailable or when you need a direct, low-cost estimate of cell concentration.

• Using the total cells counted instead of the mean cells per square
• Forgetting to include the dilution factor when the sample was diluted before counting
• Applying the 10^4 factor without using the standard hemocytometer chamber depth and large-square area