Bourbon whiskey must be distilled to no more than 160 proof and entered into barrels at no more than 125 proof.
These limits are part of the U.S. legal definition of bourbon. The mash must contain at least 51% corn, the spirit must be stored in new charred oak containers, and the finished product must be bottled at a minimum of 80 proof. Bourbon may be produced anywhere in the United States; it is not legally restricted to Kentucky.
The proof limits preserve a meaningful connection between the distillate and the grain mash while allowing barrel maturation to develop color and flavor. Producers may choose lower distillation or barrel-entry strengths for stylistic reasons.
Bourbon is often confused with Tennessee whiskey or rye whiskey. Tennessee whiskey generally follows bourbon’s core legal framework but is identified with Tennessee production and commonly charcoal filtration. Rye whiskey must use at least 51% rye rather than corn.