Unit of alcohol
One unit of alcohol is defined as 10 millilitres (7.9 grams) in the United Kingdom, and as 12.7 millilitres (10 grams) in Australia. In both countries, a so-called standard drink contains one unit of alcohol (according to the country’s own definition). The definition of a "standard drink" varies significantly in other countries.
In the United Kingdom, the number of units contained in a typical serving of an alcoholic beverage is publicised and printed on bottles.
The number of UK units of alcohol in a drink can be determined by multiplying the volume of the drink (in millilitres) by its percentage ABV, and dividing by 1000.
The formula uses ml ÷ 1000. This results in exactly one unit per percentage point per litre, of any alcoholic beverage.
Since 4% can be expressed as .04, .04 × 568 ml gives the amount of alcohol in terms of ml—which, when divided by 10, shows the number of units.
When the volume of an alcoholic drink is shown in centilitres, determining the number of units in a drink is as simple as volume × percentage (converted into a fraction of 1).
Thus, 75 centilitres of wine (the contents of a standard wine bottle) at 12% ABV contain:
It is often stated that a unit of alcohol is supplied by a small glass of wine, half a pint of beer, or a single measure of spirits. Such statements may be misleading because they do not reflect differences in strength of the various kinds of wines, beers, and spirits.
- A half pint (284 ml) of beer with 3.5% ABV contains almost exactly one unit; however, most beers are stronger. In pubs in the United Kingdom, beers generally range from 3.5%–5.5% ABV, and continental lagers start at around 5% ABV. A pint of such lager (e.g., 568 ml at 5.2%) contains almost 3 units of alcohol rather than the oft-quoted 2 units.
- Stronger beer (6%–12%) may contain 2 units or more per half pint.
- A half litre (500 ml) of standard lager or ale (5%) contains 2.5 units.
- One litre (1000 ml) of typical Oktoberfest beer (5.5%–6%) contains 5.5–6 units of alcohol.
- A medium glass (175 ml) of 12% ABV wine contains around two units of alcohol. However, British pubs and restaurants often supply larger quantities (large glass ≈ 250 ml), which contain 3 units. Red wine may have a higher alcohol content (on average 12.5%, sometimes up to 16%).
- A 750 ml bottle of 12% ABV wine contains 9 units. Some port wines may contain 20% ABV or more, which is 15 units of alcohol per bottle.
- A 750 ml bottle of 14.5% ABV wine contains 10.88 units.
- A small glass (50 ml) of sherry, fortified wine, or cream liqueur (≈20% ABV) contains about one unit.
- Most spirits sold in the United Kingdom have 40% ABV or slightly less. In Great Britain, a single pub measure (25 ml) of a spirit contains one unit.
- However, a larger 35ml measure is increasingly used (and in particular is standard in Northern Ireland), which contains 1.4 units of alcohol.
- Most alcopops contain 1.4–1.5 units per bottle. For example, a normal 275ml bottle of WKD contains 1.4 units, whereas Bacardi Breezer and Smirnoff Ice both contain 1.5 units of alcohol.
Since 1995 the UK government has advised that regular consumption of 3–4 units a day for men, or 2–3 units a day for women, would not pose significant health risks, but that consistently drinking four or more units a day (men), or three or more units a day (women), is not advisable. 
Previously (from 1992 until 1995), the advice was that men should drink no more than 21 units per week, and women no more than 14. (The difference between the sexes was due to the typically lower weight and water-to-body-mass ratio of women.) This was changed because a government study showed that many people were in effect "saving up" their units and using them at the end of the week, a phenomenon referred to as binge drinking. The Times reported in October 2007 that these limits had been "plucked out of the air" and had no scientific basis. 
An international study of almost 6,000 men and 11,000 women found that persons who reported that they drank more than 2 units of alcohol a day had an increased risk of fractures compared to non-drinkers. For example, those who drank over 3 units a day had nearly twice the risk of a hip fracture.
- Even though the sizes of wine glasses are defined in UK law, the terms "large", "medium", "standard" etc are not defined in law.
- "Alcohol and the athlete". BUPA. Archived from the original on 2007-06-07. Retrieved 2007-07-29.
- "The Alculator".
- The volume of the drink in litres multiplied by its percentage strength in ABV give the number of units. In this case, 0.568 × 5.2 gives 2.95, i.e., almost 3 units.
- "Question:- "How much alcohol is there in WKD vodka blue?"". Retrieved 2013-04-27.
- "Sensible drinking". NIdirect Government Services. 2013. Retrieved 27 May 2013.
- "Health Effects of Alcohol". Drinkaware.co.uk. Retrieved 2013-05-27.
- Drink limits ‘useless’, The Times, 20 October 2007
- The great alcohol myth, The Guardian, 26 January 2009
- Kanis JA, Johansson H, Johnell O et al. (July 2005). "Alcohol intake as a risk factor for fracture". Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA 16 (7): 737–42. doi:10.1007/s00198-004-1734-y. PMID 15455194.