“One drink” sounds like a simple unit, but a beer can be different sizes, wine glasses are rarely measured at the table, and cocktails may contain more than one pour. A U.S. standard drink gives you a common way to compare them: each standard drink contains about 14 grams of pure alcohol. The container itself does not define the drink; the amount of alcohol inside it does.
U.S. standard drink sizes
These familiar servings each contain about one standard drink. The amounts are approximate, because alcohol strength and actual pours vary.
| Drink | Approximate serving | Alcohol content |
|---|---|---|
| Regular beer | 12 fl oz | About 5% ABV |
| Table wine | 5 fl oz | About 12% ABV |
| Distilled spirits | 1.5 fl oz | About 40% ABV |
| Malt liquor or some hard seltzers | About 8–10 fl oz | About 7% ABV |
| Fortified wine | About 3–4 fl oz | About 17% ABV |
| Liqueur or aperitif | About 2–3 fl oz | About 24% ABV |
These U.S. examples come from the National Institute on Alcohol Abuse and Alcoholism’s standard drink guide. A “standard drink” is a reference amount, not a recommendation about how much to drink. Other countries may define a standard drink differently.
A can or glass may contain more than one drink
The word “drink” in everyday conversation usually means one glass, can, or bottle. That does not necessarily equal one standard drink. For example, a 12-ounce beer at 10% ABV contains about twice as much alcohol as a 12-ounce beer at 5% ABV. A larger can adds more again. The same goes for wine poured into a large glass or a cocktail made with several shots. Sweetness, ice, or a big mixer can change the taste and size of a beverage, but they do not tell you how much alcohol was poured. Our standard drink calculator works it out from the size and ABV.
If the drink is packaged, check its label for both serving size and ABV. If it is a bar pour or a homemade cocktail and you do not know the recipe, there may not be enough information to count it accurately. You do not have to guess at a precise number: just recognize that the estimate will be uncertain.
What ABV tells you
ABV means “alcohol by volume.” It is the percentage of a beverage that is pure alcohol by volume. A higher ABV means more alcohol in the same amount of liquid. That is why a small serving of liquor can contain as much alcohol as a much larger serving of beer or wine. When comparing drinks, look at both the volume and the ABV; either one alone can give you the wrong impression.
How this relates to a BAC calculator
Standard drinks help compare amounts of alcohol, while blood alcohol concentration (BAC) is an estimate of alcohol in the blood. They are related, but they are not interchangeable. A BAC calculator also needs information such as the drinks’ size and strength, when they were consumed, and body details. This site’s BAC calculator lets you enter individual drinks and their times, then shows an estimated BAC over time.
It is still only a formula-based estimate, not a breath or blood test. Two people can have different BACs after drinking similar amounts, and a drink count cannot show how impaired someone is. Do not use a BAC estimate to decide whether it is safe to drive. If you have been drinking, arrange a sober ride.
Learn more about alcohol content
For examples by beverage type, see our guides to alcohol content in different drinks, beer, wine, and shots.