In the United States, the modern definition of alcohol proof is twice the percentage of ABV. 86-proof whiskey is 43% alcohol by volume. Most vodka is 40 percent alcohol, or 80 proof. Alcohol Wipes 6x6cm 75% Isopropyl Alcohol Antibacterial Wipes Surface Disinfectant Wipes Pack of 100 So, vodka that contains 30 percent alcohol would be 60 proof. Vodka containing 60 percent of the total volume in alcohol is 120 proof. 100-proof whiskey is 50% alcohol by volume. A liquor’s proof is calculated by doubling the percentage of alcohol in the liquid. Alcohol Proof Example: An alcoholic beverage that is 40% ethyl alcohol by volume is referred to as being '80 proof'.