How is alcohol measured

One unit of alcohol is 10 ml by volume, or 8 g by weight, of pure alcohol. For example:

• One unit of alcohol is about equal to:
  • half a pint of ordinary strength beer, lager or cider (3-4% alcohol by volume); or
  • a small pub measure (25 ml) of spirits (40% alcohol by volume); or
  • a standard pub measure (50 ml) of fortified wine such as sherry or port (20% alcohol by volume).
• There are one and a half units of alcohol in:
  • a small glass (125 ml) of ordinary strength wine (12% alcohol by volume); or
  • a standard pub measure (35 ml) of spirits (40% alcohol by volume).

But remember, many wines and beers are stronger than the more traditional ordinary strengths. A more accurate way of calculating units is as follows: the percentage alcohol by volume (% abv) of a drink equals the number of units in one litre of that drink. For example:

• Strong beer at 6% abv has six units in one litre. If you drink half a litre (500 ml) – just under a pint – then you have had three units.
• Wine at 14% abv has 14 units in one litre. If you drink a quarter of a litre (250 ml) – two small glasses – then you have had three and a half units

Armed with this info, a responsible drinker gets an idea when to say no more.

Dr. Ajay Sati.