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Alcohol proof

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Title: Alcohol proof  
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Alcohol proof

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 74 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 1
  • Governmental regulation 2
    • European Union 2.1
    • United Kingdom 2.2
    • United States 2.3
    • Canada 2.4
  • See also 3
  • References 4
  • External links 5


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 1213 that of water, or 923 kg/m3, and equivalent to 57.15% ABV.[1] The term originated in the 16th century, when payments to British sailors included rations of rum.[2] 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".[3] 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".[4] The gunpowder test was officially replaced by a specific-gravity test in 1816.[3]

The value 57.15% is very close to the fraction 47 = 0.5714. Thus, the definition amounts to declaring that 100° proof spirit has an ABV of 47. From this, it follows that to convert the ABV (expressed as a percentage, as is standard, rather than as a fraction) to degrees proof, it is only necessary to multiply by 74 = 1.75. Thus pure, 100% alcohol will have 100×(74) = 175° proof, and a spirit containing 40% ABV will have 40×(74) = 70° proof.

The proof system in the United States was established around 1848 and was based on percent alcohol rather than specific gravity. 50% alcohol was defined as 100 proof.[3]

The use of "proof" as a measure of alcohol content is now mostly historical. Today, liquor is sold in most locations with labels that state its alcohol content as its percentage of alcohol by volume (ABV).

The term "percent proof" has no meaning: alcoholic strength should be stated as "degrees proof" (UK) or "proof" (US) if the respective "proof" scale is being used, or "percent ABV" if it is expressed as a percentage.

Governmental regulation

A bottle of 151 proof ("over-proof") rum.

European Union


  • The Sikes Hydrometer; A Tradition since 1816

External links

  1. ^ a b c d
  2. ^
  3. ^ a b c
  4. ^
  5. ^
  6. ^
  7. ^
  8. ^ Canadian Food Inspection Agency - Alcoholic Beverages
  9. ^ Drug Library: Canadian Government Commission - Alcohol, item 61


See also

Officially, Canada follows U.S. usage in labeling by percentage of alcohol by volume.[8] However, the old UK proof standard is still used casually: "Over-proof rum" means greater than 100° UK proof, i.e. > 57% alcohol v/v. E.g., the most common spirits at 40% ABV are 70° proof in Canadian usage and "100 proof spirits" are 57% ABV.[9]


In the United States, alcohol content is measured in terms of the percentage of alcohol by volume. The Code of Federal Regulations (27 CFR [4-1-03 Edition] §5.37 Alcohol content) requires that liquor labels must state the percentage of ABV. The regulation permits, but does not require, a statement of the proof provided that it is printed close to the ABV number.[7] For bottled spirits over 100 ml containing no solids, actual alcohol content is allowed to vary within 0.15% of ABV stated on the label.[1] Alcohol proof in the United States is defined as twice the percentage of alcohol by volume. Consequently, 100-proof whiskey contains 50% alcohol by volume; 86-proof whiskey contains 43% alcohol.[1] In the United States the term "degrees proof" is normally not used. For example, 50% ABV would be described as "100 proof" rather than "100 degrees proof".

United States

“Gay-Lussac scale previously used by much of mainland Europe, was adopted by all the countries in the European Community in 1980. Using the OIML scale or the Gay-Lussac scale is essentially the same as measuring alcohol by volume except that the figures are expressed in degrees, not percentages.”[6]
“In common with other spirits, which had been used in Britain for over 160 years.”[1]

Since 1 January 1980, the United Kingdom has used the ABV standard to measure alcohol content, as prescribed by the European Union.

United Kingdom

. A preference for one method over the other is not stated in the document, but if alcohol strength by volume is used, it must be expressed as a percentage (%) of total volume, and the water/alcohol mixture must have a temperature of 20 °C (68 °F) when measurement is done. The document does not address alcohol proof or the labeling of bottles. mass and by volume provides standards for measuring alcohol strength by [5]

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