Another way of specifying the amount of alcohol is alcoholic proof, which is twice the alcohol-by-volume number.
In the United States, many states regulate and tax alcoholic beverages according to alcohol by weight(ABW), expressed as a percentage of total mass.[8] Some brewers print the ABW (rather than the abv) on beverage containers, particularly on low-point versions of popular domestic beer brands.
Alcohol percentage by weight is only 4/5 of alcohol percentage by volume (e.g., 3.2% ABW is equivalent to 4.0% abv).[9]
Alcohol tables;: Giving for all specific gravities, from 1.0000 to 0.7938, the percentages of absolute alcohol, by weight and volume, and of proof spirit, Otto Hehner, J. & A. Churchill, ASIN B0008B5HOU