Proof

Strength

Proof is a US measure of alcohol strength that equals twice the ABV, so 80 proof means 40% alcohol.

US proof (TTB): Twice the ABV, measured at 60 F
80 proof: 40% ABV
100 proof: 50% ABV
Old British 100 proof: About 57.1% ABV
US minimum for whisky and vodka: 80 proof (40% ABV)

What proof means

You will see proof on American bottles, where it sits next to the ABV if the maker lists it. Each degree of US proof equals 0.5% ABV, so 80 proof is 40% and 100 proof is 50%. Whiskey and vodka sold in the US must be at least 80 proof.

Some people read proof as a percentage, so 42 proof sounds like 42%. It is not. Divide 42 proof by 2 and you get 21% ABV. Anything at 100 proof is 50% alcohol, and anything above 100 proof is overproof.

Proof has an older history. Under the old British Sikes scale, 100 proof was set at just over 57% ABV. The US later defined proof as exactly twice the ABV, so British and US proof numbers do not match. Check which scale a number uses before you compare two bottles.

How to work out proof from ABV

Proof and ABV describe the same strength, so a single multiplication or division converts between them.

1.Multiply the ABV by 2 to get US proof. A spirit at 40% ABV is 80 proof.
2.Divide the proof by 2 to go the other way. 42 proof is 21% ABV.
3.Count each degree of US proof as 0.5% ABV, so 100 proof is 50%.
4.Check the label for ABV first, because US labels must show it and proof is optional.

Proof compared

ABVABV is the percentage of alcohol by volume. US proof is that number doubled.
OverproofOverproof means stronger than 100 proof, which is above 50% ABV on the US scale.
British proofThe old British scale put 100 proof at about 57.1% ABV, so the two systems do not agree.

Related terms

Put it to use in your next drink

Garçon explains every step as you make the drink.