The term originated in the UK. "Proof spirit" was defined as a spirit or alcohol with a gravity of 12/13 that of water - it got the name because the sailors used to be paid with rum, and they "proved" it had not been watered down by pouring it over gunpowder and testing to see if the gunpowder would still ignite.
It's 70 proof. Therefore, 35% is its alcohol content. Alcohol content is: proof divided by 2
In the United States, the alcohol-by-volume proof measurement equates to twice the percentage of alcohol content. If a beverage contains 28% alcohol by volume, it would be considered to be 56 proof.
Proof is always double the actual alcohol content of a given product. A seventy proof vodka would contain 35% of pure (100%) ethanol.
100% pure alcohol is 200 proof. So 100 proof is 50% alcohol.
Everclear is listed at 180 proof, or 90% alcohol per vol.
1 ounce = 28.3495 grams; 200 alcohol proof = 100% alcohol content. 2 ounces of 80 proof (40% alcohol) whiskey would be 56.699 grams of whiskey with 22.6796 grams of pure alcohol.
The proof is 50 per cent of the alcohol content. 80 proof is 40% alcohol.
On the label
The alcohol content of Goldschlager is 43.5% or 87 proof. Originally the alcohol content was 53.5% or 107 proof. It is a liquer with tiny flakes of gold that float within the liquid, but which only measure up to 13mg per litre.
Dewar's whiskey has a 40% alcohol/volume, it is 80 proof.
It's a 100 proof alcohol, and 50% alcohol content.
40 proof alot