A hemocytometer gives you a count of cells in a known volume of liquid, and what you usually want out the other end is cells per millilitre. This calculator does that arithmetic: total cells counted, how many squares those cells came from, and what you diluted the sample by.
It is for the bench side of a lab session, when you have a haemocytometer under the microscope, a notebook full of tally marks, and a tube you diluted before loading. Three numbers in, one number out, in scientific notation.
Honest detail: the output is written the way JavaScript writes small and large numbers, so 750,000 comes back as 7.5000e+5. Read it as 7.5 followed by five zeros. Paste it into a report like that and a marker will stop and think, so convert it first.
Calculate cell concentration from hemocytometer counts. Enter the total cell count, number of squares counted, and dilution factor.
How it works
Three fields. Total cell count is the number of cells you tallied across everything you counted, not per square. Number of squares counted is how many of the grid’s large squares you loaded and counted, and it has to be at least 1. Dilution factor is what you multiplied by to get the loading volume from the original sample, which is 1 if you did not dilute at all.
The calculation is (count / squares) x dilution x 10,000. The division gives an average per square, the dilution factor scales it back to the undiluted sample, and the 10,000 is pure geometry: each large square is 1 mm by 1 mm with a 0.1 mm depth under the coverslip, so it holds 0.1 microliters, and there are 10,000 of those in a millilitre.
Leave anything blank, or enter a square count or dilution of zero, and it refuses with a plain message instead of guessing. Reset clears all three fields. The result itself is one line: cell concentration in cells per millilitre, four decimal places, scientific notation.
A worked example
You count 150 cells across 4 large squares, and you loaded a 1:2 dilution. That is 150 / 4 = 37.5 cells per square, times 2 = 75, times 10,000 = 750,000 cells/mL, shown as 7.5000e+5.
Same count with no dilution: 150 cells in 4 squares, dilution 1, gives 37.5 x 10,000 = 375,000 cells/mL, printed as 3.7500e+5. Halving the dilution halves the answer, which is the check worth running in your head before you trust the field.
Now a denser one. 45 cells in 3 squares with a 1:10 dilution: 45 / 3 = 15, times 10 = 150, times 10,000 = 1,500,000 cells/mL, or 1.5000e+6. And the floor case, 24 cells in 4 squares undiluted, gives 6 x 10,000 = 60,000 cells/mL, printed as 6.0000e+4. Four inputs, four very different cell densities, one formula.
Where the number goes wrong
The arithmetic is never the error. The error is in what you counted. Cells clump, and a clump of four counted as one cell quietly drops your result. Air bubbles under the coverslip mean part of the chamber was never there to count. Loading too much or too little changes the depth, and the 0.1 mm figure assumes the chamber is full and level.
Squares matter more than people expect. Four squares is the common minimum; one square gives you a number that swings a lot between runs. If you counted the 25 small squares inside one large square, that is still one large square: enter 1, not 25, or your answer is 25 times too big.
It also does no viability. Every cell you ticked is counted, live or dead, because the tool has no way of knowing. Trypan blue exclusion and the live/dead split are yours to do before the numbers arrive. There are no replicates, no averaging, no spread either, so if you ran the count twice and got 1.5e+6 and 1.9e+6, both are in the notebook and neither is checked here.
Other tools
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- Honours GPA Requirement — what your remaining credits need to hit
- IB Predicted Points — turn component scores into a predicted total
Frequently asked questions
What should I enter for dilution?
The factor you multiplied by to turn the original sample into what you loaded. Diluted 1 part sample with 9 parts diluent is 1:10, so enter 10. No dilution at all is 1. If the number is below 1 the tool rejects it, since a dilution cannot shrink your concentration.
How many squares should I count?
Four large squares is the usual compromise between speed and repeatability. Two is thin, one is a rough guess. Count more squares when the cells are sparse, because a handful of cells spread over one square gives a number that will not repeat tomorrow.
Why is my answer in scientific notation?
Because cell concentrations run into the millions and writing 1,500,000 takes space. 1.5000e+6 means 1.5 with the decimal moved six places right. Multiply it out before it goes in a thesis table, and remember the four decimals are display precision, not accuracy.
Does it count dead cells?
Yes, everything you tallied counts. This is arithmetic on your tally, not a microscope. Do the live/dead staining and the separation yourself, then run the tool on whichever total you are reporting.
Can I use it for particle counts or yeast?
Anything you count in a chamber of known depth works, as long as the squares really are 1 mm by 1 mm at 0.1 mm deep. Yeast and blood cells are the usual candidates. Other chambers with different geometry need a different factor, so do not borrow the 10,000 blindly.