Reading a Bourbon Label: Straight, Bottled-in-Bond, Mash Bill, Proof, and Age Statement

Short answer: A few words on a bourbon label are defined by federal law. These include bourbon, straight, bottled in bond, barrel proof, and the age statement. Once you know the definitions, you can tell a lot about how a bottle was made without trusting any marketing. Other popular words, such as small batch, single barrel, wheated, and high-rye, aren't defined in the federal labeling rules, and the mash bill usually isn't on the label at all.

Definitions below come from the federal standards of identity (27 CFR part 5), enforced by the Alcohol and Tobacco Tax and Trade Bureau (TTB). Checked October 26, 2026.

What every bottle has to tell you

Under the federal labeling rules, three items must appear in the same field of vision, meaning one side of the bottle: the brand name, the class or type (for example, "Straight Bourbon Whisky"), and the alcohol content. The name and address of the bottler or distiller and the net contents can appear anywhere on the container. TTB also lists the age statement (when required) and the health warning as mandatory.

"Bourbon": the legal minimum

All whisky has to meet the general federal standard. It must be distilled from a fermented mash of grain at less than 190 proof, stored in oak barrels (corn whisky is the exception), and bottled at no less than 80 proof (40% alcohol by volume).

Bourbon whisky adds tighter rules:

• Grain: a fermented mash of at least 51% corn.
• Distillation: at 160 proof or less.
• Barrels: stored in charred new oak barrels, entering the barrel at 125 proof or less.
• No additives: no neutral spirits. The table allows harmless coloring, flavoring, or blending materials for several whisky types "except for bourbon whisky."
• Made in the USA: "The word 'bourbon' may not be used to describe any whisky or whisky-based distilled spirits not distilled and aged in the United States."

Two common myths fall apart here. First, bourbon doesn't have to come from Kentucky. It has to be distilled and aged in the United States. Second, plain "bourbon whisky" has no minimum aging time in the table. It only has to go into charred new oak. A minimum age comes with the word "straight," or with an age statement.

If a state appears in the designation, it means something. Under the same standard, a state name in the designation is allowed only if distillation and any required aging happened there. The regulation's own example: "New York Bourbon Whisky" must be distilled and aged in New York. Separately, the rules require bourbon and several other American whisky types to show the state of distillation somewhere on the label. It may appear in a "distilled by" line, in the address, or as a separate "Distilled in [State]" statement.

"Straight": at least two years, nothing added

Straight bourbon whisky meets all of the bourbon rules above. It is also stored in charred new oak barrels for a minimum of 2 years, and the table allows no neutral spirits and no coloring, flavoring, or blending materials. The regulation calls "straight" "a further designation of a type, and is optional." A distillery can meet the standard and still choose not to print the word.

A straight whiskey can be a mix of straight whiskies of the same type, but the rules on where they come from are specific. Under the table, a mixture of straight bourbons distilled in different states, or one that contains coloring, flavoring, or blending material, becomes a "blended straight bourbon whiskies" product.

"Blended bourbon whisky" is looser: at least 51% straight bourbon on a proof-gallon basis, with the rest allowed to be other whisky or neutral spirits.

Age statements: what the number means, and what no number means

Under the federal definitions, age is the time the spirit spent in oak barrels after distillation and before bottling. For bourbon and most straight whiskies, only time in charred new oak counts.

• It's the youngest whisky. For a whisky with no neutral spirits, the age statement gives "the age of the youngest whisky in the product," in the form "___ years old." A "6 years old" bourbon can contain older whiskey, but none younger.
• Understating is allowed, overstating isn't. The rules permit understating a product's age and prohibits overstating it.
• Under four years means an age statement is required. An age statement is required for any whisky aged less than 4 years, "unless the whisky is labeled as 'bottled in bond.'" For older whiskies the statement is optional.

That third rule is the useful one when you shop. A straight bourbon with no age statement has to be at least 2 years old to be straight. Because whiskies under 4 years need an age statement, a compliant straight bourbon label with no age statement implies the youngest whiskey in it is at least 4 years old. That's our reading of the two rules together, not a sentence in the regulation.

"Old" in a brand name isn't an age claim.

Proof, ABV, and "barrel proof"

Proof is twice the ABV. The federal definition gives proof as the ethyl alcohol content at 60°F, "stated as twice the percentage of ethyl alcohol by volume." So 50% ABV is 100 proof, and 45% ABV is 90 proof.

ABV is the required number. Proof is optional. The alcohol content must be stated as a percentage by volume, in a format such as "40% alc/vol." Proof may also appear, but only in the same field of vision as the ABV statement. The labeled ABV has a tolerance of plus or minus 0.3 percentage points.

"Barrel proof" and "cask strength" have a specific meaning. These terms are allowed only when the bottling proof is no more than two degrees lower than the proof of the spirit when it was dumped from the barrels. "Original proof," "original barrel proof," or "entry proof" are stricter. They mean the proof going into the barrel and the proof in the bottle are the same.

Bottled-in-Bond: a 129-year-old quality rule

The Bottled-in-Bond Act of 1897 let distillers bottle spirits in a bonded warehouse under the supervision of a U.S. government storekeeper. The Act barred "any mingling of different products, or of the same products of different distilling seasons," and barred adding or removing any substance to change the spirit's original character. It allowed reducing the spirit with pure water only, to 100 proof for domestic sale. Cases had to be marked with the distiller's real name, the distillery number, and the year and season of distillation.

Today the federal labeling rules govern the term. A spirit may say "bottled in bond," "bonded," or similar only if it is:

1. the same kind of spirit, distilled from the same class of materials;
2. distilled in one distilling season by one distiller at one distillery. A season is January–June ("spring") or July–December ("fall");
3. stored for at least 4 years in wooden containers;
4. unaltered except by filtration, chill proofing, or similar physical treatments that leave nothing in the product;
5. reduced in proof with pure water only; and
6. bottled at exactly 100 proof (50% ABV).

A domestic bonded label must also show the real name or trade name of the distillery, plus the plant number where the spirit was distilled and the plant number where it was bottled. A bonded bourbon still has to meet the bourbon standard. "Bonded" adds the one-season, one-distillery, four-year, 100-proof rules on top.

The four-year rule is in today's regulations. We didn't find a four-year storage requirement in the text of the 1897 Act itself, so we credit the current regulation for it.

Mash bill: the recipe that usually isn't on the label

A mash bill is the grain recipe. For bourbon, the only legal requirement is at least 51% corn. The rest is commonly rye or wheat plus malted barley. The mash bill isn't among the mandatory label items, so you usually find it on the distillery's own website, if the distillery publishes it.

Two examples, quoted from the producers' own sites:

• Four Roses publishes two mash bills. Mash bill B is 60% corn, 35% rye, and 5% barley. Mash bill E is 75% corn, 20% rye, and 5% barley. Four Roses says it combines them with five proprietary yeast strains to make ten bourbon recipes.
• Maker's Mark says it is "made with soft red winter wheat (instead of the usual rye)." Its own pages, as we read them, don't give percentages, so we don't either.

That's where the shorthand comes from. "High-rye" bourbon uses a larger share of rye, like Four Roses' B mash bill. "Wheated" bourbon uses wheat instead of rye, like Maker's Mark. Neither term appears in 27 CFR part 5, so there's no legal threshold. If a percentage matters to you, look for it on the producer's site.

Words that sound official but aren't defined

We searched the full text of 27 CFR part 5 and found no definition for "small batch," "single barrel," "wheated," or "high-rye." These terms describe the producer's own practice. They can be accurate, and the federal rules bar label statements that mislead consumers about age, origin, identity, or other characteristics, but the regulations set no batch size or rye percentage. Ask the producer what a term means for its bottle.

A quick label checklist

1. Read the type line. "Straight bourbon whisky" is the strict category. "Blended bourbon whisky" can include neutral spirits.
2. Check the age. The number is the youngest whiskey. With no number on a straight bourbon, the youngest whiskey is likely 4 or more years old.
3. Look for "bottled in bond." It means one season, one distillery, at least 4 years, and 100 proof.
4. Find the ABV. Proof is double the ABV. "Barrel proof" means no more than 2 proof points of dilution after the barrel was dumped.
5. Find the state of distillation. It's in the "distilled by" line or a "Distilled in" statement.
6. Check the producer's site for the mash bill. The label rarely tells you.

Glassware and books for comparing labels side by side

[AFFILIATE: Glencairn whisky glass | merchant TBD]

[AFFILIATE: Norlan whisky glass | CJ]

[AFFILIATE: beginner bourbon or American whiskey reference book | Bookshop.org or Amazon]

Sources (accessed 2026-10-26)

• eCFR, 27 CFR part 5, section 5.1: Definitions (age, distilling season, proof) — ecfr.gov (section 5.1)
• eCFR, 27 CFR part 5, section 5.63: Mandatory label information — ecfr.gov (section 5.63)
• eCFR, 27 CFR part 5, section 5.65: Alcohol content — ecfr.gov (section 5.65)
• eCFR, 27 CFR part 5, section 5.66: Name and address (straight whiskies; state of distillation) — ecfr.gov (section 5.66)
• eCFR, 27 CFR part 5, section 5.74: Statements of age, storage, and percentage — ecfr.gov (section 5.74)
• eCFR, 27 CFR part 5, section 5.87: "Barrel proof" and similar terms — ecfr.gov (section 5.87)
• eCFR, 27 CFR part 5, section 5.88: Bottled in bond — ecfr.gov (section 5.88)
• eCFR, 27 CFR part 5, section 5.122: Misleading statements or representations — ecfr.gov (section 5.122)
• eCFR, 27 CFR part 5, section 5.143: Whisky (standards of identity) — ecfr.gov (section 5.143)
• Bottled-in-Bond Act (Mar. 3, 1897) — original 1897 text, scanned (PDF)
• TTB, Distilled Spirits Labeling — ttb.gov
• TTB, Beverage Alcohol Manual (TTB notes it hasn't been updated for the current part 5 rules) — ttb.gov
• Four Roses, "Our Process" (mash bills B and E) — fourrosesbourbon.com
• Maker's Mark, "Our Story" (soft red winter wheat) — makersmark.com

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