The Federal Standards of Identity for Distilled Spirits state that bourbon made for U.S. consumption must be:
- made from a grain mixture that is at least 51% corn
- aged in new, charred-oak barrels
- distilled to no more than 160 (U.S.) proof (80% alcohol by volume)
- entered into the barrel for aging at no more than 125 proof (62.5% alcohol by volume); and be
- bottled (like other whiskeys) at 80 proof or more (40% alcohol by volume).
Bourbon that meets the above requirements, has been aged for a minimum of two years, and does not have added coloring, flavoring, or other spirits may (but is not required to) be called straight bourbon.
- Bourbon that is labeled as straight that has been aged under four years must be labeled with the duration of its aging.
- Bourbon that has an age stated on its label must be labeled with the age of the youngest whiskey in the bottle
Whiskey sold as Tennessee whiskey is also defined as bourbon under NAFTA and at least one other international trade agreement, and is required to meet the legal definition of bourbon under Canadian law, but some Tennessee whiskey makers do not label their product as bourbon and insist that it is a different type of whiskey when marketing their product.