Standard Drinks Calculator — alcohol units in a drink

How it works

Because beer, wine and spirits differ so much in strength, the size of a drink alone doesn't tell you how much alcohol it contains. The NIAAA fixes a common yardstick: one US standard drink = 14 grams (about 0.6 fl oz) of pure alcohol. To find how many standard drinks are in any beverage:

Grams of alcohol = volume (fl oz) × 29.5735 × (ABV ÷ 100) × 0.789

Standard drinks = grams of alcohol ÷ 14

Here 29.5735 converts fluid ounces to millilitres, ABV (alcohol by volume) is the percentage on the label, and 0.789 g/mL is the density of ethanol. The elegance of the standard-drink idea is that very different servings can carry the same amount of alcohol: a regular beer, a glass of wine and a single shot are all about one standard drink. Conversely, a large glass of wine, a strong craft beer or a generously poured cocktail can quietly be two or more.

Knowing your standard-drink count helps you track intake against health guidelines — but note what this calculator does not do: it does not estimate your blood-alcohol concentration or whether you are safe to drive. Those depend on body weight, sex, time, food and individual metabolism.

Worked example

A 12 fl oz beer at 5% ABV:

• Grams of alcohol = 12 × 29.5735 × 0.05 × 0.789 ≈ 14 g
• Standard drinks = 14 ÷ 14 = 1.0

Now take a 12 oz craft beer at 10%: the grams double to about 28, so it counts as 2 standard drinks — the same-size glass, twice the alcohol.

Frequently asked questions

What is a standard drink?

In the US, a standard drink is any beverage containing about 14 grams (0.6 fl oz) of pure alcohol. Examples include a 12 oz beer at 5%, a 5 oz glass of 12% wine, and a 1.5 oz shot of 40% spirits.

How do I calculate standard drinks?

Multiply the volume in fluid ounces by 29.5735, by the ABV as a fraction, and by 0.789 to get grams of alcohol, then divide by 14. For a 12 oz 5% beer that gives 14 g, or one standard drink.

Does a bigger glass mean more standard drinks?

Yes — standard drinks scale with both volume and ABV. A large pour or a high-ABV drink can be two or more standard drinks even though it looks like a single serving.

Does this tell me my blood-alcohol level?

No. This tool counts the alcohol content of a drink. It does not estimate blood-alcohol concentration (BAC) or impairment, which depend on your weight, sex, time elapsed, food and metabolism.

Why 14 grams?

That is the amount of pure alcohol the NIAAA defines as one US standard drink. Other countries use different amounts (for example, 10 grams in the UK and Australia), so "units" vary internationally.

How many standard drinks are in a bottle of wine?

A standard 750 mL (25.4 oz) bottle of 12% wine holds roughly 5 standard drinks. Enter the volume and ABV above to check any bottle or can precisely.