Standard Drink Calculator
Convert any drink’s volume and alcohol percentage into US standard drinks and grams of pure alcohol.
How it works
grams of alcohol = volume(mL) × ABV% ÷ 100 × 0.789 · standard drinks = grams ÷ 14
A US standard drink is defined by its alcohol content, not the size of the glass: 14 grams of pure alcohol, roughly what is in a 12 oz regular beer, a 5 oz glass of wine or a 1.5 oz shot of spirits. To find how many standard drinks any serving holds, convert its volume to millilitres, multiply by the alcohol-by-volume percentage to get the volume of pure alcohol, multiply by 0.789 (the density of ethanol) to convert that to grams, and divide by 14. This is how the same physical amount of a strong craft beer can count as far more than one drink.
Worked example
A 12 oz beer at 5% ABV: 12 oz = 354.9 mL, so alcohol = 354.9 × 5 ÷ 100 × 0.789 = 14.0 g, and standard drinks = 14.0 ÷ 14 = 1.0 — exactly one standard drink.
Sources: NIAAA — What is a standard drink?
Frequently asked questions
Why is a "standard drink" defined by grams, not glass size?
Because a small glass of spirits and a large glass of beer can carry the same alcohol. Defining a standard drink as 14 g of pure alcohol lets guidelines and calculators compare very different drinks on an equal footing.
Is a pint of craft beer one drink?
Usually not. A 16 oz pour at 7% ABV works out to roughly 2.2 standard drinks — more than double a 12 oz 5% beer. Stronger and larger servings add up quickly, which is easy to underestimate.
Do other countries use 14 grams?
No. The US standard drink is 14 g, but the UK uses 8 g units, Australia uses 10 g, and other countries differ. Always check which definition a guideline or calculator is using.
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Educational estimate, not medical advice — for clinical decisions consult a healthcare professional.