Alcohol proof is a measure of how much ethanol (alcohol) is contained in an alcoholic beverage. The term was originally used in the United Kingdom and was equal to about 1.75 times the alcohol by volume (ABV). The UK now uses the ABV standard instead of alcohol proof. In the United States, alcoholic proof is defined as twice the percentage of ABV.

The measurement of alcohol content and the statement of this content on the bottle labels of alcoholic beverages is regulated by law in many countries. The purpose of the regulation is to provide pertinent information to the consumer.

History

From the 18th century until 1 January 1980, the UK measured alcohol content in terms of "proof spirit", which was defined as spirit with a gravity of ¹²⁄₁₃ that of water, or 923 kg/m³, and equivalent to 57.15% ABV. The term originated in the 16th century, when payments to British sailors included rations of rum. To ensure that the rum had not been watered down, it was "proved" by dousing gunpowder with it and then testing to see whether the gunpowder would ignite. If it did not, then the rum contained too much water and was considered to be "under proof". Gunpowder would not burn in rum that contained less than 57.15% ABV. Therefore, rum that contained this percentage of alcohol was defined to have "100° (one hundred degrees) proof". The gunpowder test was officially replaced by a specific-gravity test in 1816.