A standard drink refers to a specific volume of an alcoholic beverage (such as a glass of wine, a can of beer, or a mixed drink with distilled spirits) that contains roughly the same amount of pure ethanol, regardless of beverage type. This concept is used to help individuals understand that different alcoholic drinks can have similar effects when consumed in their standard serving sizes.
The amount of alcohol in a standard drink varies across regions:
In Ireland, a standard drink contains 10 grams of pure alcohol (equivalent to one glass of beer, one pub measure of spirits, or 100 mL of wine).
In the UK, one unit equals approximately 8–9 grams of ethanol.
In North America, a standard drink contains around 12 grams of ethanol.
This is to say that these measurements may differ internationally, depending on local customs and beverage packaging standards.
Sources: SAMHSA_NCBI; HRB