Calculating units of alcohol is quite simple using the internet, provided you know a few basic details about a particular drink. In the U.S., liquids are measured in fluid ounces, and units of alcohol are worked out by dividing the percentage of alcohol by volume (AbV) by 33.8.
Go to the Cleave Books Units of Drink Calculator website (see Resources).
Enter the AbV percentage of the drink in the first box.
Select "USA" from the "Standard Value" drop-down menu.
Enter the amount of fluid ounces of the alcoholic drink and select "Fluid Oz. (US)" from the drop-down menu.
Click "Calculate It." Units are displayed in the "Unit Drinks" box.
All calculations of units of alcohol should be taken as a guideline only, and should not be used to calculate the amount of alcohol in someone's blood. Alcohol affects each person differently, and you should not drink if you plan to drive or operate machinery.