A liquor is any alcoholic beverage that is produced by distillation. Many liquors, such as whiskey, vodka, rum, gin, and tequila list the alcohol content of the product in terms of a its proof. The proof is a scale used to measure the amount of alcohol in a liquor. The scale goes from 1 to 200. In the United States, the actual alcohol content, by volume, is half of whatever the proof number reads, so that a 200 proof liquor is 100% alcohol and a 100 proof liquor is 50% alcohol by volume. In other words, the proof is exactly twice the percentage of alcohol that the liquor contains. A liquor that is 200 proof, by this scale, is considered an absolute alcohol and a 100 proof liquor is considered a proof spirit.
Some liquors will list the alcohol “by volume,” such as “40% alcohol by volume (ABV).” This would mean that the liquor contains 40% alcohol and 60% water and other components. Many liquors give the alcohol content in both proof and alcohol by volume. A liquor containing 40% ethyl alcohol by volume is 80 proof. ABV listings are required by law in the United States, under the code of Federal Regulations, 27CFR (4-1-03 edition). The proof of the beverage is also allowed to be listed, although not required. This is why you will always see ABV listed on liquors made in the U.S. and often both proof and ABV.
The British system is slightly different than the U.S. The British proof spirit is 100 proof, like the U.S. proof spirit, but an absolute alcohol is 175.25 proof, meaning 57% alcohol instead of 50%. Given as ratios, the U.S. proof system is 1:2 proof to alcohol by volume and the British system is 4:7, which means multiplying the alcohol content by 1.75 will give the proof of the product.
Origin of the term Proof
The term proof has been around for a long time. It began to be used before there was a reliable and accurate way to measure the alcohol content of a beverage. Therefore, gunpowder was used to “prove” the alcohol content. Although it is hard to be certain of the exact origins of this practice, one story traces the term to the practice of paying British soldiers with rum as well as money. The soldiers needed a way to prove that the rum was not watered down, so they would douse gunpowder with it and try to set it on fire. If it failed to ignite, it showed that the rum had too much water and so was under proof. For the rum to have enough alcohol to enable to gunpowder to ignite despite the water content, it needed to be at least 57% alcohol and only 43% water, so that, as above in the British system, a 100 proof rum was 57% alcohol by volume.
How much is a Drink of Alcohol?
Obviously, different types of alcoholic beverages contain different amounts of alcohol by volume. Liquors contain the most alcohol and beers (for the most part) contain the least. We often are given estimates by researchers of how many drinks are considered moderate drinking, and therefore not particularly “bad” for you (and in some ways good for you). But, a drink, in these terms is not how many shots, beers, or glasses of wine you have, it is how much alcohol you have. So how much is a drink of alcohol?
Depending on who is talking, a drink is considered to be about 1/2 ounce of alcohol (or a little more) or 12 to 15 grams of alcohol. These are both pretty much the same amounts. Remember, right now, we are talking about the amount of alcohol which is considered a drink. The actual liquor, beer, or wine will contain more liquid than 1/2 ounce, of course. Again, depending on who you ask, moderate drinking is considered one to two drinks per day, depending on whether you’re a male of female. In maximum amounts, males should limit their intake to 30 grams or less and females to 15 grams or less. Sorry, ladies, I’m just reporting what the “science” says, don’t kill the messenger. Anyway, how do you know how much alcohol, in grams, you are drinking?
I’ll skip the explanation, and give you the simple formula. All you have to do to find out how much alcohol, in grams, your drink contains is to multiply the number of ounces by the percentage of alcohol in the drink (ABV), then multiply the answer by 0.23.
A shot of whiskey or other liquor is generally considered to be 1.5 ounces. So, for an 80-proof whiskey (40% ABV) you have: 1.5 x 40 x 0.23 = 14 (grams). So a shot of 80 proof whiskey contains 14 grams of alcohol. If you know the percentage of alcohol in the beverage, which a bartender can tell you or you can read off the bottle at home, you should have no trouble figuring the alcohol, if you’re so inclined. Of course, mixed drinks with varying amounts of liquors, liqueurs, etc. could be very difficult to figure out. However, keep in mind that many cocktails actually have more alcohol than a straight drink of liquor, wine, or beer.