Alcohol By Volume
From BrewWiki
Alcohol By Volume (ABV) is simply a measure of the percentage of alcohol as measured by a percentage of the total volume of the beer. This is equivalent to the proof value of higher alcohol liquors. Beer typically has an alcohol by volume value of between 3 and 8%. Barley wine may have an ABV as high as 10% or more. Note that while the majority of the world typically quotes alcohol by volume, in the US alcohol percentage is often measured as Alcohol By Weight.
To calculate the approximate alcohol by volume, simply measure the original gravity and final gravity as a 3 digit specific gravity and apply this formula:
- ABV = (Orig_gravity - Final_gravity) * 131