Hemocytometer Cell Count Calculator
Turn hemocytometer (Neubauer) counts into cells per mL and total cells — any square size, dilution factor or trypan blue mix volumes, live/dead viability, counting error and a seeding plan with the volume to pipette.
How it works
Cells/mL = mean count per square × dilution factor ÷ square volume (mL) — for a 1 mm² large square 0.1 mm deep that is × 10⁴ · dilution = (sample + dye) ÷ sample × earlier dilution · viability = live ÷ (live + dead) × 100 · total cells = cells/mL × suspension volume · seeding volume = cells wanted ÷ cells/mL
A large square of an improved Neubauer chamber is 1 mm × 1 mm with the coverslip 0.1 mm above it, so it holds 0.1 µL — one ten-thousandth of a millilitre. Multiplying the average count per large square by 10,000 and by the dilution gives cells per millilitre of the original suspension. If you counted the smaller squares instead (the 25 centre squares used for red cells, the 16 corner sub-squares, or the tiny 0.05 mm squares), the calculator uses their volume, and the chamber-depth option covers Fuchs-Rosenthal (0.2 mm) and Petroff-Hausser (0.02 mm) chambers. For the dilution you can type the factor or the volumes you mixed — 10 µL of cells plus 10 µL of trypan blue is a factor of 2, multiplied by any earlier dilution. Turn on the live/dead option to enter unstained and blue cells square by square: viability is live ÷ (live + dead), and the concentration and seeding volume then use viable cells. Count cells touching the top and left lines but not the bottom and right, aim for 20–200 per large square and at least 100 cells in total: the Poisson counting error is 1 ÷ √N, about ±10% at 100 cells and ±5% at 400, and the coefficient of variation between squares shows whether the suspension was mixed well. The seeding plan works out how much suspension to take for one or many wells, with medium to top up to a final volume.
Worked example
Counts of 52, 48, 55 and 49 in four large squares average 51; with a 1:1 trypan blue mix (factor 2) that is 51 × 2 × 10⁴ = 1.02 × 10⁶ cells/mL, or 5.1 × 10⁶ cells in 5 mL. To seed 1 × 10⁶ cells, take 1 ÷ 1.02 = 0.98 mL (980 µL). If 4, 6, 3 and 5 blue cells were also seen, viability is 51 ÷ (51 + 4.5) = 91.9%. For six wells of 1 × 10⁵ cells in 2 mL each with 10% extra, take 0.647 mL of suspension and add 12.55 mL of medium.
Sources: ATCC — Animal cell culture guide (hemocytometer counting and trypan blue) · Hemocytometer.org — Hemocytometer calculation
Frequently asked questions
What if I counted the small centre squares?
Pick that square size in “Squares you counted” and enter the count for each small square. The 25 centre squares together equal one large square, so each one holds 4 nL and one cell per square is 2.5 × 10⁵ cells/mL.
Does the dilution factor include trypan blue?
Yes — 10 µL cells + 10 µL dye is a factor of 2. If you diluted the cells before adding dye, multiply both factors, or use “Volumes I mixed” with the earlier dilution filled in.
How do I calculate viability with trypan blue?
Count unstained (live) and blue (dead) cells in the same squares. Viability = live ÷ (live + dead) × 100. Count within 3–5 minutes of adding the dye, because live cells start taking it up over time.
How many cells should I count?
Aim for 20–200 cells per large square and at least 100 cells in total. The counting error falls with the square root of the number counted: about ±10% at 100 cells, ±7% at 200 and ±5% at 400.
Why multiply by 10,000?
One large square holds 0.1 µL, which is 1/10,000 of a millilitre, so 10⁴ converts a per-square count into cells per mL. Smaller squares or a different chamber depth change that factor, which the calculator handles.
Related calculators
For teaching and planning — verify against your lab protocol and instrument documentation.