What on earth is a “standard drink”?

I don't know how much thought you have given to the concept of what is often referred to as a “standard drink”, but, if you haven’t thought much about it, then it is most likely because you know only the local definition of it where you happen to live. Well, there are other ideas around the world, and when you read anything factual about alcohol then you need to keep this in mind.

Growing up when I did, in the 1960s and 70s, was interesting in Australia, because the culture started moving rapidly from its British heritage much more towards American culture (but ignoring the obvious excesses!). * However, Australia did differ from both of these role models by adopting the metric (SI) measurement system, rather than keeping the Imperial ones or their derivatives. For us, there was clearly not much in common between a British ounce and an American one, for example, so we needed something different.

It thus became obvious to us that the Americans and the British were sometimes talking past each other when it came to things like volumes, etc. This is the topic of this post, with regard to alcohol.

If we consult the US National Institute on Alcohol Abuse and Alcoholism (part of the National Institutes of Health), then we will find that “one standard drink (or one alcoholic drink equivalent) contains roughly 14 grams of pure alcohol” [note the non–US unit!]. Pure alcohol, in this case is often called “absolute ethanol”, in the technical literature.

So, the NIAAA states that one standard drink is found in (using US units):

12 ounces of regular beer, which is usually about 5% alcohol
5 ounces of wine, which is typically about 12% alcohol
1.5 ounces of distilled spirits, which is about 40% alcohol.

However, this does not really help us, from two points of view. First, a more practical consideration might be to know how many drinks there are in a standard wine bottle, for example, not how much alcohol there is per drink. Second, the rest of the world does not actually agree with this definition of a “standard drink”. For example, Wikipedia has a long list of the different definitions among different countries.

This second point has been known for a long time. For example, way back in 1990, Charlotte Turner had a look at: How much alcohol is in a ‘standard drink’? An analysis of 125 studies. She found quite a degree of variation in the formal published literature, which is not a Good Thing for the rest of us. I mean, how can we work out how the conclusions from these studies compare with each other?

So, the scientists then tried to work out a way to standardize things. A summary appeared in Calculating standard drink units: international comparisons, which provides a set of simple calculation rules for converting alcohol consumption data among four common so–called ‘standard drinks’, as formally used in the USA, Canada, the UK, and Australia.

The table that I have included here tries to summarize the situation (click to enlarge it). The four countries have had different definitions of how much ethanol is in their “standard drink” (the first column), although it is straightforward to convert between them (the second column). **

For our purposes here, we can convert this information to the number of “standard drinks” there would be in a standard-sized bottle of wine (Point 1 above). The main issue for us is that this differs depending on the alcohol content of the wine (%ABV). After all, if the bottle contains twice as much alcohol then there must be twice the number of alcoholic drinks in it. So, in the table I have also provided the number of drinks for a range of different wine ABV concentrations.

Note that the commonly quoted idea that there are 5 drinks per bottle of wine applies only to wine of 10% alcohol in the USA. In Australia, such a bottle is considered to contain 6 drinks, and in the UK it has more than 7 drinks. You need to keep this sort of difference in mind when reading magazines and on–line articles — the geographical source of the text really does matter, in this case.

So, you need to stay on your toes, if you are trying to regulate your drinking based on the number of drinks you have had, for example. Different people have different ideas about this, for a very good reason — cultural diversity!

In the USA, there is an online Standard Drinks Calculator that can be used, provided by the Distilled Spirits Council of the United States. However, the numbers it produces differ somewhat from those reproduced above. Another Standard Drink Calculator produces the numbers I have quoted above for Australia; and there is also one that produces the quoted values for Canadians.

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* For example, we use the words eggplant (US) not aubergine (UK), and zucchini (US) not courgette (UK). We do, however, use tap (UK) instead of faucet (US), and railway (UK) not railroad (US).

** There are reasons for these. For example, 10 grams of alcohol is considered to be how much the average human body can process in one hour.

Note: this is a somewhat different version of an earlier post of mine: A Standard Drink is not what you think it is. Also note that the Australian social move from the UK to the USA had a lot to do with the ANZUS Treaty of 1951, involving Australia, New Zealand and the USA as military allies. One consequence of this treaty was that both Australia and NZ fought alongside the USA in the Vietnam War (and also introduced the conscription of young adult males as participants), although many if not most Americans seem not to know any of this.