For convenience in calculating intakes of alcohol, a unit of alcohol is defined as 10 ml (8 g) of absolute alcohol; this is the amount in 300 ml (½ pint) beer, a single measure of spirit (25 ml) or a single glass of wine (100 ml).

The Royal College of Physicians of England set upper limits of prudent consumption of alcohol as 21 units (=168 g alcohol) per week for men and 14 units (= 112 g alcohol) per week for women; the UK Department of Health set a daily limit of 4 units for men, and 3 for women.

The method of assessing alcohol consumption has recently been updated to take account of larger measures and stronger alcoholic drinks.