Standard Drink Calculator
A US standard drink contains 14 grams of pure alcohol, no matter what you are pouring. This calculator converts any drink into standard drinks from its volume in fluid ounces and its ABV. It finds the grams of pure alcohol using the density of ethanol, divides by 14, and multiplies by how many you have had. Because beer, wine, and spirits differ in strength and serving size, counting in standard drinks is the reliable way to track intake against the US moderate-drinking definition. Enter your serving to see the count and the grams of alcohol.
Standard drink formula
Volume in ml = fluid ounces * 29.5735
Pure alcohol (g) = volume in ml * (ABV / 100) * 0.789
Standard drinks per serving = pure alcohol (g) / 14
Total standard drinks = drinks per serving * number of drinks
The constant 0.789 is the density of ethanol in grams per millilitre, and 14 grams is one US standard drink.
Standard drink notes
- One standard drink is about 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits.
- Cocktails and large pours can contain several standard drinks each.
- US moderate drinking is up to 1 drink/day for women and up to 2 for men.
- One US standard drink is roughly 1.75 UK units.
- Read the ABV from the label, as strengths vary widely.
Standard drinks: frequently asked questions
What is a US standard drink?
A US standard drink contains 14 grams (about 0.6 fluid ounces) of pure alcohol, as defined by the National Institute on Alcohol Abuse and Alcoholism. Roughly, that is 12 ounces of regular beer at 5% ABV, 5 ounces of wine at 12% ABV, or 1.5 ounces of distilled spirits at 40% ABV.
How is the number of standard drinks calculated?
First find the grams of pure alcohol: volume in fluid ounces times 29.5735 to get millilitres, times the ABV fraction, times 0.789 (the density of ethanol). Then divide the grams by 14 to get standard drinks. This calculator does all of that from your volume and ABV.
Why use 0.789 in the formula?
Ethanol is less dense than water, at about 0.789 grams per millilitre. Multiplying the volume of pure alcohol by this density converts it from millilitres to grams, which is how a standard drink is defined.
How does a standard drink differ from a UK unit?
A US standard drink is 14 grams of pure alcohol, while a UK unit is 8 grams. So one US standard drink is roughly 1.75 UK units. They are not interchangeable; use the measure that matches your country's guidance.
What are the US drinking guidelines?
The Dietary Guidelines for Americans advise that adults who choose to drink do so in moderation, defined as up to one drink per day for women and up to two for men, and that some people should not drink at all. This calculator helps you count standard drinks against that definition.
Official sources
- National Institute on Alcohol Abuse and Alcoholism: What is a standard drink?
- U.S. Department of Health and Human Services: Dietary Guidelines for Americans.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.