What Do V/V, W/W, W/V and V/W Mean?

Many of the chemical solutions have a description in their name such as V/V, W/V and W/W.  This blog post is an explanation of what these mean.

Each of these descriptions is a way of expressing the strength of a chemical solution.  The strength of a solution can be expressed by Weight, Volume or both.  It is easiest to describe each of these separately and illustrate them with an example.

V/V

V/V means Volume/Volume and is often used when you mix 2 liquids together.  For example, a 50% v/v solution would be 50% of one solution and 50% of another – equal amounts of each in terms of Volume.  Examples of these include Acetic Acid 50% v/v and Sulphuric Acid 50% v/v.

You can buy Acetic Acid on Amazon. You can also buy Sulphuric Acid on Amazon in a range of pack sizes and concentrations.

W/W

W/W means Weight/Weight.  In a solution, it infers the percentage of substances by weight.  For example, a Hydrochloric Acid 28% w/w solution means there are 280 grams of Hydrochloric Acid for every Kilogram of the solution (the remainder being water).

W/V

W/V means Weight/Volume .  This is commonly used when a solid is dissolved in a liquid. For example, a 10% w/v solution means 100 grams of one substance is present for every 1L of another.  An example of this would be Barium Chloride 10% w/v – in this solution 100 grams of Barium Chloride is present for every 1L of solution.

V/W

If a solution is V/W it means Volume/Weight.  This is the same as the example above but the other way around.

You can buy a range of chemistry books on Amazon to further enhance your knowledge of this fascinating subject.

Rich Hudson
I'm Managing Director of a leading UK chemical supplier. My company supplies most of the chemicals I blog about, you can buy them online at Chemicals.co.uk. I also keep a personal blog at RichHudson.co.uk.
Rich Hudson
Rich Hudson
Rich Hudson

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Comments

  1. Justice Chandrasekaran S says:

    This chemical blog is extremely very informative. Moreover the details like W/W , V/V , V/W have been very clearly described in very simpler terms and one can never forget. Mr.Richard Hutson has really achieved in his life really something. I appreciate him from my heart. If he permits, I would like to copy the above details and keep it for my record and immediate reference purposes. I am now working on a chemical case for writing a judgment.
    with best regards
    Justice Chandrasekaran S

  2. I see this on hydrochloric acid solutions — 20% (v/v). Now, I can understand percent by weight but this is a puzzle to me. Does 20% (v/v) mean 20 parts by volume pure HCl per
    100 parts by volume of HCl solution. How do you measure the volume of pure HCl?

    • Hi Alex,

      Your assumption is correct that the product contains 20 parts of HCl per 100 parts of solution, however the concentration of the HCl used is not 100% (that would be a gas) but 36% w/w which is a commonly available industrial grade and generally referred to as concentrated HCl. This still gives off fumes but is a liquid product. So the answer to the question is 200mls of 36% w/w HCl in 1000mls of finished solution, this gives approximately 8.2% w/w solution.

      HCl 36% w/w has an s.g. of 1.18 which means 1000mls weighs 1180g. 36% of this is pure HCl, therefore 36% of 1180 = 424.8g or 424.8 grams per litre of HCl. If we take 200mls of 36% w/w HCl we are taking 424.8 x 0.2 grams of pure HCl which equals approx. 85g pure HCl, this 85g is then diluted to 1L.

      So in terms of w/w there are 200mls x 1.18 =236g plus approx. 800mls of water (s.g. of 1), giving 1036g in total. 85g of pure HCl in this total weight gives (85/1036) x 100 = 8.2% w/w.

      Hope this helps!

      • Craig Day says:

        It appears that your definition of “v/v” is incorrect. It would work in your example of mixing 2 dilute acids, but when a liquid like alcohol is mixed with water, the volumes are not additive, so 50 mL of alcohol plus 50 mL of water does not equal 50% v/v alcohol, since the total solution volume is less than 100 mL. Please clarify. Thanks.

  3. I need a help! I am working with a polymer (PEI). Commercially it is available in solution and product say- it is 50% w/v in H2O. But, it is so viscous, that, I need to dilute it more. Now the confusion start- If I add x gm into 100 ml, what will be final concentration then?!

    Please help!

  4. solomon liatu says:

    Please how many grams of PEG 6000 do I need to prepare 10% and 20% of PEG and how can I prepare this!

  5. it really helps me

  6. Dear Sir,

    I want to make Pain Killer Oil using methyl salicylate ,camphor,eucalyptus oil,etc.
    Can u give me the exact weight wise formulation to make it easy for me to make

    Thanks and Regards

    Arif Khalak

    • Dear Arif,

      Unfortunately we can’t recommend you mixing a solution of this sort yourself, so cannot give any advice with regards to measurements.
      Please contact a chemical supplier who can blend the ingredients safely and accurately for you.

      Thanks

  7. Rahul Shukla says:

    I have been thinking of whats the meaning of W/W w/v as it is written on most of the
    ‘AYURVEDIC PAIN RELIEF OINTMENT’ (I am Indian) which I usese a lot.
    and today I searched it over the internet and found THE CORRECT AND COMPLETE INFORMATION on your BLOG. and after reading the desired information, as I scrolled your blog I Found it is filled with LOTs And LOTs of information ……..which is pretty cool and good .
    your blog is excellent . I APPRICIATE IT….. THNX.

  8. Thank you for this very useful blog!!

  9. Hi!

    You really helped me to understand this, it’s so simple.

    thank you so much.

  10. Thanks for the information

  11. Phillip J. Fry says:

    A very reader-friendly post!

    However, I see a correction to be made on w/v:

    Instead of “present for every 1L of water,” it should be “present for every 1L of SOLUTION” since you never add a fixed amount of water (due to the errors caused by varying density of different compounds).

    Keep posting though, thank you for your help!

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