Because there is no international definition of a “standard drink,” it is important to quantify the amount of pure ethanol consumed in grams. The amount is calculated by multiplying the % ABV by the volume consumed (in mL) and the density of ethanol (0.789 g/mL at 20°C). In the United States, one standard drink contains 14 g of ethanol, which is equivalent to a 12-oz beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of spirit (40% ABV). For example, one standard drink of beer in the US is the product of ABV of the beer, volume of the drink, and alcohol density [(5ml of alcohol /100 ml) × 355 mL × 0.789 g/mL] corresponding to 14 g of ethanol. This formula can be used to define an ethanol dose (e.g., grams of ethanol per kilogram of body mass), which is useful in blood alcohol concentration (BAC) estimations (6).
