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Difference between percent alcohol and proof

Updated April 17, 2017

Labels on alcoholic beverages often disclose a measurement of the alcohol content of the product, but not everyone knows how to interpret that information. A bottle of wine may be labelled as 8 percent abv, while a distilled spirit may be described as 80 proof. The difference between alcohol percentage and proof is simple to calculate, and once you know how to do it, you won't be left guessing in the grocery store aisles again.

Chemical overview

In organic chemistry there are actually many different molecules that fall under the category of alcohol, characterised by the presence of one or more hydroxyl, or oxygen-hydrogen, groups. The alcohol found in beverages is ethyl alcohol, also commonly known as ethanol, drinking alcohol, pure alcohol or grain alcohol. It is a small alcohol molecule, with a molecular formula of C2H6O.

Measurements

Alcohol by volume, or abv, is a percentage that expresses how many millilitres of alcohol are present for every hundred millilitres of liquid at 20 degrees C Celsius. Alcohol proof is expressed by doubling the per cent alcohol of a beverage. Absolute alcohol is 100 per cent alcohol by volume, or 200 proof, which is highly toxic.

Examples

Fermented beverages have lower alcohol percentages because the yeast that causes fermentation cannot survive in high alcoholic content. Beer ranges from 4 to 6 per cent alcohol, typically, meaning it is 8 to 12 proof. The alcohol by volume, or abv, in wine may range between 7 and 14 per cent, or 14 to 28 proof. Distilled alcohol, though, is present in much higher concentrations, ranging from 40 to 95 per cent alcohol by volume, or 80 to 190 proof.

Volume taxation

One of the reasons why it is important for distributors and retailers to specify the alcohol content of beverages is for tax purposes. Volume taxes, also called per unit taxes, are those that are imposed based on the amount of alcohol present in a product. The higher the alcohol content, the higher the volume taxes.

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About the Author

Deborah Meister is a biologist in California who has been writing about science and nature since 2010. Her articles appear on eHow and Answerbag. Meister received her Bachelor of Science in biology from California Polytechnic State University, San Luis Obispo, where she concentrated her studies in field and wildlife biology and botany.