What is 1 unit of alcohol?

In the United Kingdom, a unit of alcohol is defined as 10 millilitres (or approximately 8 grams) of ethanol (ethyl alcohol). This is approximately the amount of ethanol an average healthy adult can breakdown in an hour. It is used as a basis for guidelines on consumption of Alcoholic Beverages; the number of units contained in a typical drink is publicized and marked on bottles.

In the US, a unit is considered to be 14 grams (17 ml) of pure alcohol -- about 0.6 fluid ounces or 1.2 tablespoons). The UK and US figures fall at either end of the range of average alcohol metabolism in one hour.