Hemocytometer Calculator
cells/mL = cells counted ÷ squares counted × dilution × 10^4. Count, enter the dead cells, and the hemocytometer calculator gives viability and the volume to seed.
Viable cells per mL
- Viable cells per mL 208 live cells ÷ 4 squares × 2 × 10,000. Each large square holds 0.1 µL, so the 4 counted hold 0.4 µL.
- 1,040,000
- Total cells per mL Live and dead: 220 ÷ 4 × 2 × 10,000.
- 1,100,000
- Viability 208 unstained of 220 counted. Trypan blue enters cells whose membranes are damaged, so blue cells are counted as dead. Count within a few minutes of mixing, because the dye slowly enters live cells too.
- 94.5%
- The formula The improved Neubauer chamber's large squares are 1 mm × 1 mm with the coverslip 0.1 mm above them: 0.1 mm³, which is 0.1 µL or 10^-4 mL. Dividing by 10^-4 mL is multiplying by 10^4.
- cells/mL = cells counted ÷ squares × dilution × 10,000
- Average per large square If one square differs greatly from the others, the cells were clumped or the chamber was unevenly loaded. Mix and reload rather than average it away.
- 55
- Viable cells in 10 mL 1,040,000 per mL × 10 mL.
- 1.04 × 10^7
- Volume for 500,000 viable cells 500,000 ÷ 1,040,000 per mL.
- 481 µL
- Counting precision Cell counts follow Poisson statistics: the error on a count of N is √N, so 220 cells is good to about ±6.7%. This is the floor; pipetting and loading add to it.
- ±6.7% (1 SD), about ±13.2% at 95%
| Cells wanted | Volume to take |
|---|---|
| 10,000 | 9.62 µL |
| 50,000 | 48.1 µL |
| 100,000 | 96.2 µL |
| 250,000 | 240 µL |
| 500,000 | 481 µL |
| 1,000,000 | 962 µL |
| 5,000,000 | 4.81 mL |
| 1.00 × 10^7 | 9.62 mL |
- Decide how to treat cells on the boundary lines before you start. A common convention is to count cells touching the top and left lines and ignore those touching the bottom and right, so each boundary cell is counted once rather than twice or not at all.
- Do not overfill the chamber, and load it in one smooth flow: a flooded or dried chamber does not have the 0.1 mm depth the formula assumes.
- Viability by trypan blue is a membrane-integrity test only. It does not measure whether cells will attach, divide or behave normally.
How the Hemocytometer Calculator works
The formula:
cells per mL = (cells counted ÷ squares counted) × dilution factor × 10^4
A worked example, the one above: cells mixed 1:1 with trypan blue (a dilution factor of 2), 220 cells counted across the four large corner squares, 12 of them blue. That is 55 cells per square, and 55 × 2 × 10^4 = 1,100,000 cells per mL in total. The 208 unstained cells give 52 × 2 × 10^4 = 1,040,000 viable cells per mL, and viability is 208 ÷ 220 = 94.5%. In 10 mL of suspension there are 10.4 million viable cells, and seeding 500,000 of them takes 0.481 mL.
Where 10^4 comes from. It is the chamber's geometry, not a fudge factor. The standard improved Neubauer hemocytometer is ruled in squares of 1 mm × 1 mm, and the coverslip sits 0.1 mm above the grid. One large square therefore holds 1 × 1 × 0.1 = 0.1 mm³, which is 0.1 µL or 10^-4 mL. Cells per square divided by 10^-4 mL is cells per square × 10^4. The large center square is divided further into 25 small squares, each 0.2 mm × 0.2 mm, holding 0.004 µL; counting those multiplies by 2.5 × 10^5 instead. Use them only when the sample is too dense to count in the large squares.
The dilution factor. It is total volume over sample volume. Equal volumes of cells and 0.4% trypan blue is a factor of 2, which is why that 2 appears in nearly every cell-culture count. If you diluted the cells first, multiply the two: 1 in 5 in medium, then 1:1 in dye, is 10. Forgetting the dye dilution is the most common error, and it halves every result.
Viability. Trypan blue is excluded by intact membranes and taken up by damaged ones, so blue cells are counted as dead. Viability is unstained cells over all cells. It is a membrane test only, and the dye slowly enters living cells too, so count within a few minutes of mixing.
How many cells to count. Cells land in the squares at random, so a count follows Poisson statistics: a count of N has a standard deviation of √N, and a relative error of 1 ÷ √N. Count 25 cells and the answer is uncertain by ±20%; count 100 and it is ±10%; count 400 and it is ±5%. That is why the usual advice is to count at least about 100 cells, across more squares or both chambers if the sample is sparse. The precision row shows where your count stands. Pipetting and loading errors come on top of it.
Seeding. The volume to take is the number of cells wanted divided by the concentration. Seed on the viable count, not the total, or every plate will be short by the fraction that is dead.
What this calculator does not do: decide what density to seed at, which depends on the cell line and the experiment, or replace an automated counter's own calibration.
Hemocytometer Calculator FAQ
How do you calculate cells per mL from a hemocytometer?
Divide the cells counted by the number of large squares counted, multiply by the dilution factor, then by 10^4. 220 cells in 4 squares with a 1:1 trypan blue dilution is 220 ÷ 4 × 2 × 10^4 = 1.1 million cells per mL.
Why multiply by 10,000?
Each large square of an improved Neubauer chamber is 1 mm × 1 mm × 0.1 mm deep, which is 0.1 µL, or 10^-4 mL. Dividing a per-square count by 10^-4 mL is the same as multiplying by 10^4.
How do you calculate cell viability with trypan blue?
Viability = unstained cells ÷ total cells × 100. With 208 clear cells out of 220 counted, viability is 94.5%. Trypan blue enters cells with damaged membranes, so the blue cells are counted as dead.
What is the dilution factor for trypan blue?
Mixing equal volumes of cell suspension and trypan blue is a dilution factor of 2. If the cells were diluted before that, multiply: diluted 1 in 10 and then mixed 1:1 with dye is a factor of 20.
How many cells should I count on a hemocytometer?
At least about 100. Counting error is Poisson, roughly 1 ÷ √N, so 100 cells gives about ±10% and 25 cells ±20%. Count more squares or both chambers if the sample is sparse.