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Standard Drink

General

Standard Alcoholic Drink Unit

A standardized measure of pure alcohol content — 14 grams in the US — used to compare alcohol content across beer, wine, and spirits regardless of serving size.

Definition

A standard drink is a fixed, standardized measure of pure alcohol content used to make it possible to compare and track alcohol consumption consistently across different beverage types — beer, wine, and spirits — regardless of the size of the glass, can, or bottle they're served in. In the United States, one standard drink equals 14 grams (about 0.6 fluid ounces) of pure ethanol.

Standard drinks are used to:

  • Communicate consistent, comparable alcohol guidelines across beverage types
  • Estimate blood alcohol content (BAC) from consumption history
  • Support public health guidance on low-risk drinking limits
  • Help individuals track actual alcohol intake rather than just "number of drinks," which varies enormously by container and strength

Because a large craft beer, a full glass of wine, and a mixed cocktail can all contain very different amounts of actual alcohol, the standard drink unit normalizes them into one comparable measure.

Formula

Standard Drinks = (Volume in fl oz × ABV% × 0.789) ÷ Grams per Standard Drink

Where 0.789 g/mL is the density of pure ethanol, and grams per standard drink is 14g in the US (8g in the UK, 10g in Australia).

Simplified, for the US definition:

Standard Drinks = (Volume in fl oz × ABV%) ÷ 0.6

Worked Example

A 750 mL bottle of wine at 13% ABV (approximately 25.4 fl oz):

Standard Drinks = (25.4 × 0.13) ÷ 0.6 = 3.30 ÷ 0.6 = 5.5 standard drinks

Interpretation: A typical bottle of wine at 13% ABV contains about 5.5 US standard drinks — useful context when comparing to the recommended daily limit of 1-2 standard drinks. Use the standard drink calculator to convert any beverage, size, and strength.

Key Things to Know

  • Container size is not a reliable guide: A "glass of wine" or "a beer" can vary 2-3x in actual alcohol content depending on pour size and ABV, which is exactly why the standard drink unit exists — count grams of alcohol, not containers.
  • Definitions vary internationally: The US (14g), UK (8g "units"), and Australia (10g) all define a standard drink differently, so guidelines and drink-counting apps should always be checked against the correct national definition.
  • Craft beer and high-ABV cocktails contain more than one "drink" worth of alcohol: A 16 oz craft IPA at 8% ABV contains roughly 1.7 standard drinks, not 1, despite being served as a single beverage.
  • Standard drinks feed directly into BAC estimates: Blood alcohol content calculations use grams of alcohol consumed (derived from standard drink counts), body weight, sex, and time elapsed — accurately counting standard drinks is the first step to any BAC estimate.
  • Guidelines are expressed in standard drinks for a reason: Public health recommendations on "low-risk" drinking are always given in standard drink units precisely so they remain valid regardless of what specific beverage someone is drinking.

Related Calculators

Standard Drink Calculator →Calculate how many US standard drinks (14g pure alcohol each) are in any beverage from its volume and ABV percentage. A quick reference for tracking alcohol intake.

Related Terms

BACBlood Alcohol ContentPack-YearPack-Year Smoking History

Frequently Asked Questions

In the US, one standard drink contains 14 grams (0.6 fluid ounces) of pure alcohol. This is roughly equivalent to 12 ounces of regular beer (5% ABV), 5 ounces of wine (12% ABV), or 1.5 ounces of distilled spirits (40% ABV / 80 proof). Use the [standard drink calculator](/standard-drink-calculator/) to convert any beverage, volume, and alcohol percentage into standard drinks.
There is no international consensus on what constitutes a standard drink — the US defines it as 14 grams of pure alcohol, the UK uses 8 grams (called a 'unit'), and Australia uses 10 grams. This means the same physical drink (e.g., a pint of beer) can count as a different number of 'standard drinks' depending on which country's definition is applied, so it's important to check which standard a source is using.
Multiply the volume in fluid ounces by the alcohol by volume (ABV) percentage, then multiply by the alcohol density factor (0.789 g/mL), and divide by the grams-per-standard-drink for your country (14g in the US). A typical 750mL bottle of 12% ABV wine contains about 5 US standard drinks. The [standard drink calculator](/standard-drink-calculator/) handles this conversion automatically for any bottle size and alcohol percentage.
US Dietary Guidelines suggest that if alcohol is consumed, it should be limited to 2 drinks or fewer per day for men and 1 drink or fewer per day for women, with many health authorities now recommending less overall given cancer and cardiovascular risk research. These guidelines are all expressed in standard drink units precisely because container size and alcohol strength vary so much between beverages.
Standard drinks are one of the key inputs used to estimate [Blood Alcohol Content (BAC)](/glossary/bac/), since BAC calculations need to know the actual grams of pure alcohol consumed rather than just the number of 'drinks' by container. A standard drink count of 3 beers is not the same alcohol exposure as 3 shots of hard liquor unless both are converted to grams of alcohol using the standard drink formula first.