A pint of Guinness is equal to 2.3 units of alcohol. One unit of alcohol is equal to 10 milliliters of pure alcohol. In the United States, the term used is "standard drink," and one standard drink is equal to 0.6 fluid ounce of pure alcohol.
As alcoholic beverages have different percentages of alcohol per volume, one unit or one standard drink of a certain type of drink may differ in size to another. One standard drink of regular beer is 12 fluid ounces, while for table wine, only 5 fluid ounces give the same amount of alcohol. For hard liquors, such as brandy, the volume of one standard drink is even less at only 1.5 fluid ounces.