The alcohol content of mixed drinks varies greatly, and the potency of a specific drink can vary according to the recipe and the person making it.
It's easy to determine the alcohol content by volume (ABV) of a drink if you know the ingredients and the amount of each. It's simply a matter of calculating the amount of pure alcohol in each ingredient, summing these and dividing by the total volume of liquid.
Multiply the amount of each spirit by its percentage of alcohol. The ABV of any liquor is listed on the label, as this is required by law.
For example, to mix a Harvey Wallbanger, you might use 1.25 ounces vodka, 3 ounces orange juice and 0.5 ounce Galliano. Assume the labels show that the vodka contains 40 percent ABV and the Galliano contains 30 percent ABV.
For the vodka, multiply 1.25 ounces x 40 percent = 0.5 oz of alcohol (40 percent is expressed in decimal form as 0.40).
Similarly, for Galliano, multiply 0.5 ounce x 30 percent = 0.15 ounce of alcohol.
Write the amounts of alcohol on a piece of paper.
Sum the amounts of alcohol. In the example, 0.5 + 0.15 = 0.65 ounce of alcohol.
Add the total volume of each ingredient in the drink. Include both alcoholic and non-alcoholic ingredients.
In the example, 1.25 ounces vodka + 3 ounces orange juice + 0.5 ounce Galliano = 4.75 ounces.
Divide the total alcohol by the total volume of liquid.
In the example, divide 0.65 ounce alcohol by 4.75 ounces total liquid. This equals 0.136. Move the decimal two places to the right to express this as a percentage. The drink in the example contains 13.6 percent ABV.
- Gauge your alcohol consumption by determining the number of standard drinks you have consumed. The National Institute of of Alcohol Abuse and Alcoholism defines a standard drink as one containing 14 grams (about 0.6 fluid ounce) of pure alcohol. This is equivalent to a 12-ounce bottle of beer at 5 percent ABV or 6 ounces of wine at 10 percent ABV.
- In the example, divide .65 (ounces of alcohol) by .6 to determine the equivalent number of standard drinks. 0.65 divided by 0.6 = 1.1 standard drinks.
- Do not include the volume of ice or foam when determining ABV.
- The National Institute of of Alcohol Abuse and Alcoholism recommends that men consume no more than four drinks in a day and 14 drinks in a week. Women are advised to consume no more than two drinks per day and seven drinks per week.
Jim Dorsch has been a writer and editor since 1991. He has written for major newspapers, including "The Washington Post" and "Chicago Tribune," and is publisher and editor of "American Brewer" magazine. He holds a Bachelor of Science in mathematics from Rose-Hulman Institute of Technology and a Master of Science in statistics from Purdue University.
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