What Is a Standard Drink?
This calculator uses the United States definition of a standard drink: any beverage containing 14 grams (about 0.6 fluid ounces) of pure alcohol. Because beers, wines, and spirits differ wildly in strength, comparing them by container size is misleading. Converting to standard drinks lets you compare a can of beer, a glass of wine, and a shot of liquor on an equal footing. Note: other countries use different units (e.g., the UK uses 8 g units, Australia uses 10 g), so adjust if you are outside the US.
How to Use It
Enter the volume of the drink in milliliters and its alcohol by volume (ABV) as a percentage — both are usually printed on the label. The calculator returns the number of US standard drinks, plus the volume and mass of pure alcohol it contains.
The Formula Explained
First, multiply the volume by the alcohol fraction (ABV ÷ 100) to get the volume of pure ethanol. Multiply that by ethanol's density, 0.789 g/ml, to convert volume into grams. Finally divide by 14 g — the mass of alcohol in one US standard drink:
$$\text{Standard Drinks} = \frac{\text{Volume (ml)} \times \dfrac{\text{ABV (\%)}}{100} \times 0.789}{14}$$
Worked Example
A 355 ml can of beer at 5% ABV: pure alcohol volume = \(355 \times 0.05 = 17.75\) ml. Mass = \(17.75 \times 0.789 \approx 14.01\) g. Standard drinks = \(14.01 \div 14 \approx 1.0\) standard drink. That is exactly why a typical 12-oz beer is considered one drink.
FAQ
Why 0.789? That is the density of ethanol at room temperature in grams per milliliter, used to convert alcohol volume to alcohol mass.
How many standard drinks in a 750 ml bottle of 12% wine? \(750 \times 0.12 \times 0.789 \div 14 \approx 5.07\) standard drinks.
Is this a measure of how drunk I'll get? No. Standard drinks only count alcohol content. Blood alcohol concentration also depends on body weight, sex, food, and time. Always drink responsibly.
