Unit of alcohol

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A large glass of red wine contains about three units of alcohol

In Britain a unit of alcohol is defined as 10 millilitres (or approximately 8 grams) of ethanol (ethyl alcohol). It is used as a basis for guidelines on consumption of alcoholic beverages; the number of units contained in a typical drink is publicised and marked on bottles.

1 Formula
2 Quantities
3 Limits
4 See also
5 References

[edit] Formula

The number of 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 (or litres × % abv).

Thus a pint (568ml) of beer at 4% ABV contains

$\frac{568 \times 4}{1000} = 2.3\mbox{ units}$

In the metric system there is 1 unit per percentage point of ABV in 1 litre of a drink; e.g., 37.5 units in a litre of a typical whisky with 37.5 ABV.

[edit] Quantities

It is often misleadingly stated that a unit is supplied by a small glass of wine, half a pint of beer, or a single measure of spirits.^[1] Such statements are misleading because they do not reflect the large differences in strengths and measures of wines, beers and spirits.^[2] ^[3]

[edit] Beers

A half pint (284ml) of ordinary strength (3.5-4% ABV) beer contains about one unit. However, some beers are stronger. In pubs, beers generally range from 4% to 5.5% ABV with continental lagers starting at around 5% ABV. A pint of such lager (568ml at 5.2% for example) is almost 3 units of alcohol, rather than the often-quoted value of 2 units per pint.
A 500ml can/bottle of standard lager (5%) generally contains around 2.5 units.
'Super-strength' or strong pale lager may contain as much as two units per half pint.

[edit] Wines

A small glass (125ml) of 8% abv wine contains one unit, or 8 g (0.25 oz) of alcohol. However, British pubs and restaurants usually supply larger quantities (medium: 175 ml or large: 250 ml), and few wines are as weak as 8%; 12% is more typical. A standard pub measure (medium glass - 175 ml) of white wine (at 12%) contains around 2 units (actually 2.1) and a large glass (250 ml) contains 3.0 units. Red wine, which usually has a higher alcohol content (up to 16%), contains for an average 14% abv. an alcohol content of 3.5 units for a large (250 ml glass), approximately one-sixth higher than a typical white wine. Just two bottles of 14% abv. red wine a week will supply the maximum intake of alcohol for a man recommended by UK health guidelines.
A 750ml standard bottle of 12% wine contains 9 units. Many wines (especially New World red wines) may contain 14% ABV or more, which is 10.5 units of alcohol per bottle.

[edit] Fortified wines, etc.

A small glass (50ml) of sherry, fortified wine, or cream liqueur (approx. 20% abv) contains about one unit.

[edit] Spirits

Most spirits sold in the UK have 40% ABV or slightly less. A single pub measure (about 25ml) of such a spirit contains one unit. However, a larger single measure of 35 ml is now often sold, resulting in the consumption of 1.4 units of alcohol.

[edit] Limits

Since 1995 the UK government has advised that regular consumption of between three and four units a day for men and between two and three 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[1]. Previously (from 1992 till 1995) the advice was that men should drink no more than 21 units per week, and women no more than 14.^{[citation needed]} 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,^{[citation needed]}a phenomenon referred to as binge drinking. The difference between sexes is given due to the (typically) lower weight and water-to-body-mass-ratio of women.

It was claimed in October 2007 that these limits had been "plucked out of the air" and have no scientific basis.^[4]

An international study (Kanis, 2005) 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.^[5]