A standard drink is a fixed amount of pure alcohol, not a fixed glass size. In the United States, one standard drink holds 14 grams of pure alcohol. That same 14 grams can arrive as a beer, a glass of wine, or a shot of spirits, because each pour is sized to match.
A US standard drink contains 14 grams of pure alcohol, which equals 0.6 fluid ounces. The classic matches are 12 oz of 5% beer, 5 oz of 12% wine, and 1.5 oz of 40% spirits. Larger pours or stronger drinks hold more than one standard drink.
What Counts as One Standard Drink
In the United States, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines one standard drink as 14 grams of pure alcohol. That is the same as 0.6 fluid ounces of pure alcohol. The number is about the alcohol itself, not the size of the cup.
This fixed amount is a counting tool. It lets you compare a beer, a wine, and a cocktail on one scale, even though the glasses look nothing alike. When you know how many standard drinks you had, you can also estimate blood alcohol with a BAC calculator.
One warning up front: a standard drink is a measuring unit, not a safety limit. It tells you how much alcohol is in a glass. It does not tell you that any number of drinks is safe for you, and it never tells you that you are safe to drive.
The Three Standard Drink Equivalents
The short version: a regular beer, a glass of wine, and a shot of spirits can each be one standard drink. They look very different, yet each delivers the same 14 grams of pure alcohol. The trick is that stronger drinks come in smaller pours.
Here are the NIAAA reference pours. A 12 oz beer is weak but large. A 1.5 oz shot of spirits is tiny but strong. The serving size falls as the alcohol by volume (ABV) rises, so the grams stay level at 14.
How to Count the Grams of Alcohol
The short answer: multiply the volume by the strength, then by the weight of alcohol. The formula is grams of alcohol = volume in mL x (ABV / 100) x 0.789. The 0.789 is the density of ethanol, meaning one milliliter of pure alcohol weighs 0.789 grams.
Try it on the 12 oz beer. First, 12 fluid ounces is about 354.9 mL. Then 354.9 x 0.05 x 0.789 lands on 14 grams. The same math gives 14 grams for the 5 oz wine and the 1.5 oz shot, which is exactly why those three pours all count as one standard drink.
Once you know your standard-drink count, drop it into the BAC calculator to see a rough blood alcohol estimate. Use it for learning only, never to decide whether to drive.
Why ABV and Serving Size Matter
Here is where many people undercount. A real-world pour is often bigger or stronger than the reference. When that happens, one glass can hold two drinks worth of alcohol, even though it looks like a single serving.
Take a 16 oz (473 mL) craft beer at 7% ABV. Run the formula: 473 x 0.07 x 0.789 = about 26.1 grams. Divide by 14, and that single can is about 1.9 standard drinks, almost double the 12 oz, 5% reference. A tall, strong pour quietly raises the count.
Wine does the same thing. A 25 oz (750 mL) bottle at 13% ABV works out to about 76.9 grams, or roughly 5.5 standard drinks in the whole bottle. So a “couple of glasses” poured by hand can add up faster than the label suggests. The table below shows common pours next to the reference.
| Drink | Size and ABV | Grams of alcohol | Standard drinks |
|---|---|---|---|
| Reference beer | 12 oz at 5% | 14 g | 1.0 |
| Reference wine | 5 oz at 12% | 14 g | 1.0 |
| Reference shot | 1.5 oz at 40% | 14 g | 1.0 |
| Large craft beer | 16 oz at 7% | 26.1 g | about 1.9 |
| Full wine bottle | 25 oz at 13% | 76.9 g | about 5.5 |
Not sure of a drink’s strength? Check the label, or work out a blend with the ABV calculator. Curious about the energy side of a drink? See how many calories are in alcohol.
How Standard Drinks Feed a BAC Estimate
Standard drinks are the input that blood alcohol math needs. A BAC estimate starts from the total grams of alcohol you drank, which is just your standard-drink count times 14. From there, body weight, sex, and time since your first drink shape the estimate.
This is why counting correctly matters. If you log a 16 oz craft beer as one drink instead of 1.9, your BAC estimate will read far too low. Accurate counting keeps the estimate honest, which you can explore in the health calculators hub.
Please read: A standard-drink count and any BAC estimate are rough learning tools, not safety guarantees. Everyone processes alcohol differently, and impairment can begin before any legal limit. Never use these numbers to decide whether to drive. If you have been drinking, use a sober driver, a taxi, or a rideshare.
FAQs About Standard Drinks
How many grams of alcohol are in one standard drink?
A US standard drink holds 14 grams of pure alcohol, which equals 0.6 fluid ounces. This fixed amount is what lets you compare a beer, a wine, and a shot of spirits on one shared scale.
Is a standard drink the same as one glass or one can?
No. A standard drink is a fixed amount of alcohol, not a fixed glass. One can, bottle, or poured glass can hold more than one standard drink when it is larger or stronger than the reference pour.
Why do beer, wine, and spirits all count as one drink?
Because the reference pours are sized to match. A 12 oz beer, a 5 oz wine, and a 1.5 oz shot each deliver about 14 grams of alcohol. The serving shrinks as the strength rises, so the grams stay level.
How many standard drinks are in a 16 oz craft beer?
A 16 oz craft beer at 7% ABV holds about 26.1 grams of alcohol. Divided by 14, that is roughly 1.9 standard drinks, nearly double the 12 oz, 5% reference beer. A tall, strong pour counts for more.
How do I calculate grams of alcohol myself?
Multiply the volume in milliliters by the ABV divided by 100, then by 0.789, the density of ethanol. For a 354.9 mL beer at 5%, that is 354.9 x 0.05 x 0.789, which gives 14 grams.
Why does a full bottle of wine count as so many drinks?
A 25 oz bottle at 13% ABV holds about 76.9 grams of alcohol, roughly 5.5 standard drinks. Hand-poured glasses are often larger than 5 oz, so a bottle adds up faster than it looks.
Can counting standard drinks tell me I am safe to drive?
No. Counting drinks only estimates how much alcohol you drank. It cannot confirm you are safe to drive, since impairment can start before any legal limit. The only safe amount of alcohol before driving is zero.
Sources and Further Reading
References Used in This Article
- National Institute on Alcohol Abuse and Alcoholism (NIAAA). What Is a Standard Drink? Accessed October 5, 2026.
- Centers for Disease Control and Prevention (CDC). About Impaired Driving. Accessed October 5, 2026.
- MultiCalculators. BAC Calculator (Widmark estimate). Accessed October 5, 2026.
- MultiCalculators. ABV Calculator. Accessed October 5, 2026.
This article is general education, not medical advice. The numbers here are general guidance, not personal targets. Talk to a healthcare provider about your own health. Reviewed for accuracy by Dr. Abdullah Khalil, MBBS. Last updated 2026-10-05.
Author
Shakeel Muzaffar is the Founder and Editor-in-Chief of MultiCalculators.com, bringing over 15 years of experience in digital publishing, product strategy, and online tool development. He leads the platform's editorial vision, ensuring every calculator meets strict standards for accuracy, usability, and real-world value. Shakeel personally oversees content quality, formula verification workflows, and the platform's commitment to publishing tools that are genuinely useful for students, professionals, and everyday users worldwide.
