Proof to ABV Converter
| Drink | ABV % | Proof | Note |
|---|---|---|---|
| Beer | 5 | 10 | labels ABV only |
| Wine | 12 | 24 | labels ABV only |
| Vodka, gin, rum, most whiskey | 40 | 80 | the US default |
| Bottled-in-bond bourbon | 50 | 100 | the 1897 legal floor |
| Overproof rum (151) | 75.5 | 151 | more than half alcohol |
| Grain alcohol ceiling | 95.6 | 191 | distillation azeotrope |
American proof is the simplest conversion in the liquor aisle: proof is exactly twice the percentage of alcohol by volume, so an 80 proof vodka contains 40% ABV and a 100 proof bourbon carries 50%. Type either number and the other appears - useful for comparing a European bottle labeled only in ABV with an American one labeled in proof, or for working out what 'cask strength' actually means on your shelf.
The doubling dates to 1848, when the United States simplified an older and much fussier British standard: the original proof test involved soaking gunpowder with rum and seeing if it still burned, a threshold that worked out near 57% ABV. America skipped the gunpowder and halved the number. The UK abandoned proof entirely in 1980 and labels ABV only - which is why a London bottle reads 40% where a Nashville one reads 80.
How to use
- Type a proof number (80) to see ABV (40%), or type an ABV percentage (40) to see the proof - both directions update live.
- Check the table for the bottles you actually meet: beer and wine label in ABV only, most American spirits in proof, cask-strength bottles in either.
- Remember the direction of surprise: a 151 proof bottle is 75.5% ABV - more than half the liquid is pure alcohol, which changes how you pour it.
Frequently asked questions
What does 80 proof mean?
80 proof means 40% alcohol by volume - US proof is defined as exactly twice the ABV percentage. It is the default strength for vodka, gin, rum and most whiskey on American shelves, and the number survives from the 1848 simplification: Congress doubled the old British proof of spirits to make the tax gauge easy. Every proof number on a US label converts by halving, nothing more.
Why is it called proof?
From the days when 'proof' had to be demonstrated with gunpowder: spirits were mixed with powder and ignited - if the powder still flashed, the spirit was strong enough to be 'proved'. The British standard that settled around this test corresponds to about 57% ABV at 100 proof, which is why historical naval rum proof numbers look strange next to American ones. The US abandoned the gunpowder legacy for a clean 2-to-1 ratio in 1848.
Is proof used outside the United States?
Barely. The UK dropped its proof system in 1980 and the EU, Australia and Canada all label ABV only, so proof numbers you meet today are almost all American - or historical. A US proof (2x ABV) and the old UK proof (roughly 1.75x ABV) are different scales, which is why a '100 proof' British naval recipe and a '100 proof' American bottle do not contain the same strength.
What is the highest proof alcohol can be?
Distillation alone tops out around 95.6% ABV (191 proof) - the azeotrope where alcohol and water distill together - which is why grain alcohol sold at 190 proof is the practical ceiling; higher concentrations only come from chemical drying. Most spirits sit far below: 40-50% ABV (80-100 proof) is the working range, and anything above 100 proof is usually labeled 'overproof' and poured with more respect.