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.

Today I’m bringing you a useful dilution factor calculator to help with those quick calculations in the lab. To calculate the dilution factor, you need two things: the original volume of the solution you dilute and the final volume after diluting (or the volume you have added to dilute, in which case the final volume will be the original volume plus the volume you have added). Input those in the two first fields below, and you’ll get the dilution factor and the dilution performed in relative notation. Choose a specific notation from the dropdown box to change it to the standard one you use. See my other post if you need more help carrying out dilutions.


    1. Hi there,

      I’ve put your numbers in and I get 111.11 as a dilution factor:

      This is assuming 45mL is your initial volume and 5L is your final volume. If 5L is the volume you add, then you would put 5.045L in the second box, and would get 112.11 as a dilution factor. Remember to change the units in the dropdown too.

      Did I miss something? Let me know if you have other questions.


  1. Hi,

    thanks Maria for u r reply.

    i need to get dilution factor as 1.67.How ?

    they mentioned as 45 ml of fortune chemical in 5 lit of water. then we will get 1.67 as dilution factor. i don’t know the concentration.

    Can you please help me?

    can you explain

    1. Hi again,

      I don’t really get it as 1.67 would be if you put 3L of the chemical into 2L of water. Are you sure those are the volumes, or are you sure 1.67 is the dilution factor you are seeking? Can you give me a link to the instructions you are following to prepare this solution? I might be able to help further then.


  2. Hi I start with the dilution 0.15 and am supposed to end up with 0.25 dilution. This gives the dilution factor 5/3.

    I don’t understand what that means, am I supposed to take 5 of the sample and 3 of the dilutent, e.g. water?

    1. Hi there,

      If 0.15 and 0.25 are dilutions, then practically what you need to do is concentrate more (not dilute). So for instance, if you have 10mL, the first dilution would require you to add 56.7mL and the second one would require you to add 30mL (it’s impossible for your to get to a more concentrated solution from a more dilute one just by adding water). There needs to be a centrifugation step in-between or something like that to allow you to concentrate more.
      If it was the other way round, e.g. the initial one is 0.25 diluted and the final one is 0.15, then you would need to add the difference between the two volumes stated above (26.7mL of water) to the 0.25 solution.

      Hope that makes sense, let me know if you have other questions.

      1. Lets say I have dilution factors from 50 to 20. Does that mean that I take e.g. 1 ml of the sample and 49 ml of water for the first one, and then 20 ml from the first one and 30 ml water. Or do I do them separately by taking 1ml sample, 49 ml water (for 50 dilution factor) and then on a new tube with 2.5 ml sample and 47.5 ml water (df=20).

        Thank you for the reply above.

  3. Hi Maria Fuentes,
    Nice website. Happy to visit this site. I have problem calculating these numbers.
    I have stock solution containing 3620 cell/microliter. (I have 10 ml of stock solution).
    I want to fill 21 tubes each having 500000 Cell/70 microliter.
    Can you simplify this and tell me the step wise calculation so that it can be used in future .
    Thank you.

    1. Hi Suchen,


      Ok so to answer your question:

      1. Calculate the final density:
      final density = 500,000 cells / 70 uL = 7,142.8 cells/uL

      2. From the stock solution, get the amount of cells needed. We will assume 22 samples here so you don’t run out of solution for your 21.
      22 tubes x 500,000 cells = 11,000,000 cells needed
      The total number of cells in the stock solution is 3620 cells/uL * 10,000 uL = 36,200,000 cells
      Volume to take from stick solution = 10,000 uL * 11,000,000 cells / 36,200,000 cells = 3,038.7 uL

      3. Now, the original solution is less dense than the final one (3620 cells/uL vs 7,142.8 cells/uL). You have to concentrate it, this is done by centrifuging the 3,038.7uL of stock solution and removing the supernatant. You can then resuspend in the right amount of fluid:
      liquid to add = 22 x 70 uL = 1,540 uL

      Hope that helped! let me know if you have other questions.


  4. Good evening Maria,
    Thanks for the calculator. I need your explanation for something still though. I’m doing an in vitro drug release test. And I’ve seen different mathematical equations all over the internet, I’m not even sure which is right. I’ll like you to confirm, using your calculator, is my final volume the volume of liquid I take out into the cuvet? Thanks

    1. Hi Bee,

      No prob, glad you find it useful.

      The dilution factor is only calculated when there is volume of liquid added to the sample. For instance, say you start with 10mL of cell suspension. You add 5mL of water, so your final volume is 15mL. Then the dilution factor is final volume over initial volume, in this case: 15mL/10mL = 1.5. In your example, the final volume is the total volume you have after adding the liquid. If you already had sample in the cuvet, then the final volume is the volume you had plus the volume you added. If you are adding an already diluted solution to the cuvet, then the final volume is the volume of fluid you had in the tube you are taking it from (and you must have performed a diution in a previous step).

      I hope that all makes sense! Let me know otherwise.


  5. Question….
    Starting with 2.25 mL distilled water
    Adding .25 mL to the 2.25 mL

    So total would be 3.25 mL

    When I put it in the calculator my dilution factor is 13 or 1:13. Can you help explain how it came to is? I do not understand how to get that answer.

    1. Hi K,
      Thanks for checking out the calculator!
      So: 2.25ml + 0.25mL = 2.5mL to start with (not 3.25mL)
      I assume you are diluting 0.25mL with the 2.25mL of distilled water, so you put 0.25mL in the initial volume box and the final volume (2.5mL) in the final volume box. You get a dilution factor of 10 (2.5/0.25).
      Does that make sense?

  6. Hi Maria

    I have cell suspension and if I add 5 ML of media in it for re-suspension. What will be the ratio? Will it be 1:5 or 1:6?


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