What Is The Relationship Between Liquor Proof And Its Alcohol Content?

What Is The Relationship Between Liquor Proof And Its Alcohol Content? 3: In the United States, the system — established around 1848 — is a bit simpler: “Proof” is straight up two times alcohol by volume. So a vodka, say, that is 40 percent ABV is 80 proof and one that is 45 percent ABV