What Is a Standard Drink?
This calculator applies to the United States. In the US, one "standard drink" is defined by the NIAAA as any beverage containing 0.6 fluid ounces (about 14 grams) of pure alcohol. Because drinks vary widely in size and strength, counting "drinks" by the glass can be misleading. This tool converts any beverage's volume and alcohol-by-volume (ABV) into the number of equivalent US standard drinks.
How to Use It
Enter the volume of your drink in fluid ounces, its ABV as a percentage, and how many of those drinks you had. The calculator returns the total number of US standard drinks, the standard drinks contained in a single serving, and the total volume of pure alcohol consumed.
The Formula Explained
The math is simple: multiply the drink volume by its ABV fraction to get the volume of pure alcohol, then divide by 0.6 fl oz to express it in standard drinks.
$$\text{standard\_drinks} = \text{volume\_oz} \times \frac{\text{ABV}}{100} \div 0.6$$
Common US references: a 12 oz beer at 5% ABV, a 5 oz glass of wine at 12% ABV, and a 1.5 oz shot of 40% spirits each equal roughly one standard drink.
Worked Example
Suppose you drink two 16 oz craft beers at 8% ABV. Per drink: $$16 \times (8 \div 100) \div 0.6 = 16 \times 0.08 \div 0.6 = 1.28 \div 0.6 \approx 2.13 \text{ standard drinks}.$$ For two of them: about 4.27 standard drinks — more than double what a "two beers" count suggests.
FAQ
Is this the same as UK units? No. The UK uses 8 g of alcohol per unit, while the US standard drink is 14 g. This tool uses the US definition.
Does it estimate blood alcohol content (BAC)? No — it only counts standard drinks. BAC also depends on body weight, sex, time, and food intake.
Why divide by 0.6? Because 0.6 fl oz is the volume of pure alcohol in one US standard drink, so dividing converts any pure-alcohol amount into standard-drink units.
