I did my PhD in the Department of Chemical Engineering at Imperial College London. My research focused on mathematical modeling of the cell cycle in leukemia and involved experiments with cell lines. During that time, I had to count cells with a hemocytometer so often to track growth that I got tired and decided to build an app, HemocyTap, and share my knowledge on the topic here to help as many people as possible.

HemocyTap is an app that I developed during the first year of my PhD because I was (literally) getting cramps in my thumbs from counting cells. The four main features that were a must for me are:

  1. Being able to see which squares I have already counted, count those squares again if I have lost track of cells in a particular square.
  2. Getting the repetitive and error-prone calculations done for me, consistently in the same way, and without the need to type anything in a calculator.
  3. Saving my counts and being able to export them via email. This was crucial as I needed those counts as part of the results sections of a scientific paper.
  4. Going back to my counts and tracking how fast cells have been proliferating in a graph, along with their doubling time

I used it (and refined it) throughout my PhD and it served me really well. Other people in my lab started using it, so I decided to make it available on iTunes. Because so many people asked for it, I also recently developed the Android version. No more going around the lab trying to find the tally counters, the lab book (or a piece of paper), the calculator… Plus, you get all your data directly in your inbox! It’s all in there, and it’s as easy as ABC. So if you’re starting out with the hemocytometer, this app can save your life. Or, if you’re experienced already, you will ask yourself how you have survived so long without it. Seriously.

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To see the app in action, check out the demo video I created:

I am open to adding any features that people find useful – send them via the form below


    1. Hi Jimmy,

      There are a few things that work differently in the app. For instance, you have the dilution instead of the dilution factor. The dilution, in the format 1:x (where 1 is the parts of cell suspension and x the parts of dilutant, usually PBS), is equivalent to the dilution factor using the formula: dilution factor = (1+x). So if you’re using for instance 1:1 in the app, you should be using a dilution factor of 2 in the online calculator.

      The other thing to double check is that the number of highlighted squares in the app corresponds to the number of squares counted in the online calculator. For example, let’s say you have counted cells in the four corner squares of two hemocytometer chambers. In the app, they would be highlighted in blue and the cell numbers you have counted would appear on top. In the calculator, you need to enter 8 (4 + 4) in the # squares counted field. Finally, for the online calculator you should select “Big squares in the corner”.

      Let me know if you still get different results and I will look into it in more detail.



      1. Hi Maria,

        Thanks for the quick response! I didn’t know that you need to un-highlight squares that are not being used from the settings. That fixed my problem.

        I noticed that in the “Subculture” part of the app, the “Volume to add” actually gives you the total volume – it doesn’t subtract the initial volume as explained here: https://www.hemocytometer.org/2013/04/09/hemocytometer-calculation/

        Can you confirm this, or am I missing something there?


        1. Hi Jimmy,

          Glad you got it working.

          Yes, that is correct. The app assumes you remove the supernatant (used medium) before adding new medium, and therefore gives you the total amount of new medium to add. If you usually keep the old medium and add new medium to it, then you are right that you should add the “volume to add” – “initial volume”. I will keep it in mind for future versions of the app.

          Thanks for your suggestion!


  1. Hello.
    Considering how thick the hemocytometer slide is, one would imagine it being difficult to view cells on the hemocytometer with an inverted microscope. However, this is not the case. I was wondering if you had any information about the optical properties of the hemocytometer slide. I looked online but did not get any information on this topic. Thanks.

    1. Hi Paul,

      I didn’t find any specific information on the topic either, but I would assume adjusting the focus by moving the plate closer to the lens corrects for the increased distance between the lens and the hemocytometer surface. Here are a couple of answers that may help: stackexchange, researchgate.



  2. Hi Maria

    I wanted to know if you could recommend a good microscope for YEAST cell counting and viability with a haemocytometer. The microscope must have the ability to fit a camera and ideally the scope would be supplied without the camera. We offer very sophisticated methods at present with a disposable haemocytometer but for the small breweries we are thinking of a low cost solution involving a good quality microscope..

    Dr John Carvell
    Aber Instruments http://www.aberinstruments.com

      1. Hi Maria
        Hope you are well.

        Have you seen the Oculyze approach to cell counting. It would be good to get your views as I will see them next week in Germany. It would be good if you could reply by email.

        best regards


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