Bourbon is a type of whiskey defined by specific legal rules in the United States: it must be mostly corn, made under certain strength limits, and aged in new charred oak barrels with no flavor additives.

Core legal requirements

For whiskey to be called bourbon in the U.S., it must:

  • Be made from a grain mash that is at least 51% corn.
  • Be distilled to no more than 160 proof (80% alcohol by volume).
  • Enter the barrel for aging at no more than 125 proof (62.5% ABV).
  • Be aged in new, charred oak containers (almost always American white oak barrels).
  • Contain no added flavors or colors; only water can be added to adjust proof.

If a bottle breaks any of these rules, it can still be whiskey, but it cannot be labeled bourbon.

Extra terms you’ll see

A few common label terms tighten the rules further:

  • Straight bourbon: Aged at least 2 years; if under 4 years, the label must state the age.
  • Kentucky bourbon: Bourbon made in Kentucky (the style itself does not legally have to be from Kentucky).
  • Wheated bourbon: Uses wheat, instead of rye, as the secondary grain in the mash bill, which often gives a softer, rounder profile.

How bourbon differs from other whiskey

Key differences versus other whiskey styles include:

  • Grain bill: Bourbon is corn‑heavy (51%+), while Scotch relies mostly on malted barley and many other whiskeys may lean on rye or other grains.
  • Barrels: Bourbon must use new, charred oak; Scotch and many other whiskies can use used barrels (often ex‑bourbon).
  • Additives: Bourbon cannot use flavorings or coloring; some other whiskies allow them under certain regulations.

Flavor impact of the rules

Those legal requirements shape how bourbon tastes:

  • High corn content tends to bring sweeter notes like caramel and corn bread.
  • New charred oak barrels add vanilla, toffee, spice, and the deep amber color.
  • Entry proof limits and no‑additive rules push producers to get character from wood and grain rather than post‑processing tweaks.

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Wondering what makes whiskey a bourbon? Learn the exact legal requirements—corn percentage, barrel rules, proof limits, and additive bans—and how they shape bourbon’s flavor and set it apart from other whiskeys.

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