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

Weight Volume

The strength of a solution can be expressed by Weight, Volume or both

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.

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 ever 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 ever 1L of water.

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.

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.

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