Units of alcohol – rational metric sizes would solve the problem

Today’s TV news carried a leading story that units of alcohol will be appearing on all bottles, cans cartons etc of alcoholic drinks. People were asked in the street what they thought of this move. Several people asked, what’s a unit?

A good question I think!

Ok it’s 10 ml of alcohol and at least its based on metric. But why invent something such that nobody will know what is stands for?

It would be far simpler if the advice given is that men should drink no more than 30 – 40 ml per day and women 20 – 30 ml. Alcoholic drinks already have percentages ABV on them and given that people generally understand percentages (or if preferred think of it as so many ml for every 100 ml), they would know how to work it out, particularly if the quantities of drink were rational metric sizes. For example a 500 ml can of beer with 4% alcohol (4 ml per 100 ml) is 20 ml alcohol. Easy!

A good case for improving metric awareness and getting rid of awkward quantities such as 440 ml, 568 ml etc

See also earlier article Units of alcohol – 18 January

Author: UK Metric Association

Campaigning for a single, rational system of measurement

7 thoughts on “Units of alcohol – rational metric sizes would solve the problem”

  1. This is a common trick used in many other disciplines. In the US alcoholic strength is still stated in proof. So, what is a proof? It means 0.5 %. So if you have 80 proof alcohol, then you have 40 %.

    If someone speaks the proof word and is asked what it means then the explanation involves converting the proof to percent. So why not just tell the percent in the first place and not be so obscure with terms that have no meaning unless converted?

    Another example is in temperature ratings of materials. Up until the ’70s, temperature classes used letters. Each letter corresponded to a different temperature a material was good for. But the letters were in no natural order. Since that time the classes have been redefined to use numbers representing the temperature rating in degrees Celsius.

    If a material is good for 180°C, then it is class180. Yet, there are still those that refer to the old letters. This usually requires an expenditure of time to research and look for a chart that does a conversion.

    So, I’m not surprised that there are still those who try to hide real numbers behind obscure terms.


  2. This is the text of a letter which I have sent to a national newspaper. Others may wish to send different letters on this topic to their favourite papers.

    “It is unfortunate that the Department of Health does not publicise the fact that a so-called “unit” of alcohol is actually a centilitre (10 millilitres). If this were better known, it would be possible for drinkers to multiply the percentage alcohol by volume (ABV) by the quantity of the drink in centilitres – e.g. 50 cl of beer at 3.8% ABV gives 1.9 cl (or “units”) of alcohol.

    However, the insistence on retaining obsolete pints (57 cl) for draught beer makes this calculation more difficult.

    Another argument for going fully metric.”


  3. The real problem with the current unit system is doesn’t take modern drinking patterns like a unit is a pint (58,6cl) of beer (2% ABV), 17,5cl of wine (8% ABV) or 2,5cl of spirits (37,5% ABV).

    The first shows it problems, most beers are now around 4% ABV not 2%, the reason is the beer chosen at the time was an English ale, not a Continental lager, like Carlsberg. It is the same with the wine, the wine that was chosen was a cheap German Liebfraumilch or Riesling, not a Australian or Californian Merlot or a Cabernet Sauvignon, which is around 13% ABV, plus it common to receive a 25cl glass rather then a 17,5cl glass.


  4. When “units” of alcohol were first introduced (1970’s), the “scaleâ€? was
    1 pint [568 mL] beer = 2 units
    1 small glass wine = 1 unit
    1 tot (1/6 gill) spirits [23.67 mL] = 1 unit.

    People were encouraged to count in units only. The measure for beer was about right (568 mL beer at 4% gives 2.3 units), the measure for spirits was about right (23.67 mL of whiskey at 40% give 0.95 units), but there was no fixed glass size for wine, so something had to be done.

    Wine was taxed very heavily at the time, it was not the source of a drink problem and landlords used small glasses because of the tax. The Government advisors suggested therefore that 1 unit was an appropriate number that could be given to the public.

    It was only in later years when the European Court of Justice ruled that the high tax on wine was an unlawful discrimination against non-UK products and ordered the UK to bring the tax on wine down that wine drinking started to become a problem.


  5. The Drinkaware site http://www.drinkaware.co.uk/how-many-units.html carries the following advice:
    “The alcohol content of drinks is measured in units. One UK unit contains eight grams of pure alcohol”

    This begs the question “Does one unit contain 8 g of pure alcohol or does it contain 10 ml of alcohol?â€? Both are close to each other – my book of tables shows that at 20ºC, ethyl alcohol has a density of 789 kg/m³. However, since 10 is a round number and all calculations involving alcohol use volume rather than mass, I regard the advice as not being particularly helpful.


  6. Further to my observations in the article above there is also the point that whilst this latest initiative will inform drinkers about their consumption of alcohol from booze in sealed containers (bottles cans etc) it wont help much with open containers (glasses, mugs and so on).

    It begs the question are they going to insist that pubs, wine bars, restaurants and any other licensed premises somehow provide that same information? If they do it brings us back to how it is calculated. Standard 568 ml beer mugs do at least have a fixed volume (albeit an awkward one) but what about all those different sized wine glasses?

    In the end people who are trying to keep tabs on how much they are drinking will have to, at some point, get their brain round the business of percentage ABV and what that means for the actual amount of alchohol (in ml) in that glass of wine they had at dinner.


  7. What’s so difficult about replacing the word “unit” with centiltre? Any wine drinker will have a gut feeling about cl as they will be used to a 75 cl bottle.

    In fact, my daughter, who has spent the last few summers in southern France and Swirtzerland is more than happy with decilitres too. She complained to me that Swiss wine glasses are a mere 1 “deci” instead of the 175 ml or 250 ml that we get over here. As a red wine drinker, I prefer a 250 ml glass containing 1 deci so I can get the bouquet properly.


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