Hemocytometer Cell Count Calculator
Turn a hemocytometer count into cells per mL. Enter the live and dead cells counted, the squares you counted and the dilution, and get the concentration, the viability, the total cells and the volume to seed or dilute.
How to Use
- Choose a mode: Concentration (cells/mL and viability), Seeding volume (how much suspension holds a set number of cells) or Dilute to target.
- Enter the live (unstained) cells and, for viability, the dead (blue) cells you counted in total across all the squares.
- Pick which squares you counted, from the 4 corner squares to the 25 small centre squares, and keep the depth at 0.1 mm for a standard improved Neubauer chamber.
- Enter the dilution factor: 2 if you mixed the cells 1:1 with trypan blue, 1 if you loaded them undiluted.
- Read the concentration in the readouts; the grid shows which squares were counted. Show Work gives each step and the counting error.
Worked Example
Concentration and viability. Cells are mixed 1:1 with trypan blue (dilution factor 2) and loaded on an improved Neubauer chamber. The 4 corner squares hold 180 clear (live) and 20 blue (dead) cells. Live per square = 180 ÷ 4 = 45, so live cells/mL = 45 × 2 × 10⁴ = 9 × 10⁵. Viability = 180 ÷ 200 × 100 = 90%.
Seeding. To put 2 × 10⁵ cells in a well, take 200,000 ÷ 900,000 = 0.2222 mL = 222.2 µL of the suspension.
The common mistake: forgetting the trypan blue dilution. Leaving out the factor of 2 gives 45 × 10⁴ = 4.5 × 10⁵ cells/mL, half the true 9 × 10⁵. You would then seed 444.4 µL instead of 222.2 µL and put twice as many cells in every well. Dividing by 9 squares when you only counted 4 is the same kind of slip: it gives 4 × 10⁵ instead of 9 × 10⁵.
Show Work
Formulas
Counting Chambers and Dye Exclusion
A hemocytometer (also spelled haemocytometer) was first a tool for counting blood cells, which is where the name comes from. In the 1870s the French histologist Louis-Charles Malassez introduced a glass counting chamber of known depth with a ruled grid, so that cells seen under the microscope could be turned into a count per volume. The ruling most labs use today carries the name of the German physician Otto Neubauer; the “improved Neubauer” pattern is the 3 mm × 3 mm grid of nine 1 mm squares drawn above, with the centre square split into 25 smaller ones for dense samples such as red blood cells.
Trypan blue comes from the azo dyes tested in the early 1900s, in the circle of Paul Ehrlich’s chemotherapy research, as drugs against trypanosomes, the parasites behind sleeping sickness, which is how it got its name. As a viability stain it works by exclusion: a living cell with an intact membrane keeps the dye out, while a dead cell lets it in and turns blue.
Automatic counting arrived with Wallace Coulter, who patented the Coulter principle in 1953: cells passing through a small hole change its electrical resistance, and each pulse is one cell. Hand counting on a hemocytometer is still the everyday check in cell culture because it is cheap and shows you the cells.
About This Tool
This calculator turns a hemocytometer count into a concentration, using the true volume of the squares you counted rather than a fixed factor, so it handles corner squares, all nine, or the small centre squares, and a chamber of a different depth. It gives the viability from a trypan blue count, the total cells in your suspension, the volume to seed a set number of cells and the volumes to dilute to a target concentration, and it warns when too few cells were counted for a reliable answer.
Everything runs in your browser; nothing you enter is sent anywhere.
Related tools: Dilution Calculator, Centrifuge RCF Calculator, and Molarity Calculator.
Frequently Asked Questions
How do you calculate cells per mL from a hemocytometer?
Divide the cells counted by the number of large squares, multiply by the dilution factor, then by 10⁴. Counting 180 live cells in the 4 corner squares after mixing 1:1 with trypan blue gives 180 ÷ 4 = 45 per square, × 2 × 10⁴ = 9 × 10⁵ live cells/mL.
Where does the 10⁴ factor come from?
Each large square of an improved Neubauer chamber is 1 mm × 1 mm and the cover slip sits 0.1 mm above it, so the square holds 0.1 mm³ = 0.0001 mL. One cell per square is therefore 10,000 cells/mL. A small centre square is 0.2 mm × 0.2 mm, holding 0.004 mm³, so its factor is 250,000 (2.5 × 10⁵).
How do I calculate cell viability with trypan blue?
Viability is live cells ÷ all cells × 100. Live cells keep the dye out and look clear; dead cells take it up and look blue. 180 clear and 20 blue cells give 180 ÷ 200 × 100 = 90% viability. The dilution does not matter for viability because it cancels out.
How many cells should I count?
Counting error follows Poisson statistics: about ±1 ÷ √N for N cells counted. Counting 100 cells gives ±10%, 400 cells ±5% and only 45 cells ±15%, so count more squares when the sample is sparse.
How much cell suspension do I need to seed 200,000 cells?
Divide the cells you want by the live concentration. At 9 × 10⁵ live cells/mL, 2 × 10⁵ cells are in 200,000 ÷ 900,000 = 0.2222 mL, or 222.2 µL. Six wells at that density need 1.2 × 10⁶ cells, which is 1.333 mL.
How do I use the Hemocytometer Cell Count Calculator?
Simply type your numbers and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Does it cost anything or need an account?
No. The tool is completely free, there is no account to create, and it keeps working offline after the page first loads.
Is anything I type uploaded?
No. The tool works entirely on your device, so the values you enter never leave your browser.
Common Use Cases
Passaging cells
Dilute a 9 × 10⁵ /mL suspension to 1 × 10⁵ /mL in 20 mL: take 2.222 mL of cells and add 17.78 mL of medium.
Seeding plates
Six wells at 2 × 10⁵ cells each need 1.2 × 10⁶ cells, which is 1.333 mL of a 9 × 10⁵ /mL suspension.
Harvest yield
A 10 mL suspension at 9 × 10⁵ live cells/mL holds 9 × 10⁶ live cells in total.
Dense samples
Yeast diluted 1:10 with 160 cells in 5 small centre squares gives 32 × 2.5 × 10⁵ × 10 = 8 × 10⁷ cells/mL.
Checking a thaw
40 clear and 5 blue cells give 88.89% viability, but with only 45 cells counted the count itself is uncertain by about ±15%.
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