Drambook field guide
What Is a Mash Bill? How the Grain Recipe Decides Whether a Whiskey Is Bourbon, Rye, or Wheated
A mash bill is a whiskey's grain recipe: the mix of corn, rye, wheat, and malted barley, given as percentages by weight, that goes into the fermenter before distillation. That recipe is what decides whether a whiskey is legally bourbon, rye, or wheated bourbon: bourbon must be at least 51% corn, rye whiskey at least 51% rye, and a "wheated" bourbon simply swaps rye for wheat as the secondary grain. Read on for the legal lines, the flavor each recipe predicts, and real bottles that show the difference.
Quick version: corn is sweetness, rye is spice, wheat is softness. The mash bill tells you which one is steering the glass before you ever taste it.
The mash bill is the recipe, written in grain
Every American whiskey starts as a mash: grains milled, cooked, and fermented into a beer that is then distilled. The mash bill is the list of those grains and their proportions. A distiller might publish a recipe as "75% corn, 15% rye, 10% malted barley," and that line tells you most of what you need to know about the spirit's intended character.
Corn is the workhorse of American whiskey because it ferments into a sweet, full-bodied spirit. Rye and wheat are the two common "flavoring grains" that sit in the second slot and shape personality. Malted barley, usually a small slice at the end, carries the enzymes that convert starch to sugar during fermentation. The percentages are not decoration; in the United States they are part of how the law defines what the bottle can be called.
The legal lines competitors usually fudge
This is where vague explainers get hand-wavy. The grain minimums are not opinion or tradition; they are written into the U.S. standards of identity for distilled spirits, in 27 CFR Part 5.143 (administered by the TTB). The relevant lines are short and exact:
- Bourbon whiskey must be made from a fermented mash of not less than 51% corn.
- Rye whiskey must be made from a fermented mash of not less than 51% rye.
- Wheat whiskey must be made from a fermented mash of not less than 51% wheat.
Bourbon carries a few more rules that the mash bill does not cover: it must be made in the United States, distilled to no more than 160 proof, entered into the barrel at no more than 125 proof, and aged in new charred oak. But the 51% corn floor is the one that puts the word "bourbon" on the label. Cross 51% rye instead and the same distillery, the same barrels, makes rye whiskey.
Note one thing that trips up beginners: "wheated bourbon" is not the same as "wheat whiskey." A wheated bourbon is still a bourbon, still over 51% corn, that happens to use wheat as its second grain. A wheat whiskey is the rarer category that is over 51% wheat. The label distinction matters, and it is exactly the kind of detail a good catalog should keep straight for you.
Wheated, high-rye, low-rye: what the secondary grain does
Once corn clears 51%, the secondary grain is where the whiskey gets its accent. There is no legal definition of "wheated," "high-rye," or "low-rye"; these are the shorthand the industry uses to describe the second grain, and most explainers agree on the rough bands and the flavor they predict.
Wheated bourbon: corn and softness
A wheated bourbon puts wheat in the secondary slot instead of rye. Wheat is a mild grain, so it does not fight the corn for attention. The result, as nearly every guide describes it, leans soft, sweet, and rounded: honey, vanilla, caramel, and a bready or pastry-like note, with little of rye's pepper. Because wheat steps back, the corn's sweetness and the barrel's oak come through more clearly. Wheated mash bills also tend to lean heavy on corn, often 70% or more, with wheat in the 15% to 20% range.
The style traces to W.L. Weller, who swapped rye for wheat to make a gentler bourbon, and it is the recipe behind the most chased bottles in the category. The Drambook catalog records the whole wheated family on a single mash bill, from everyday pours like Weller Special Reserve up through Weller 12 Year and the allocated Pappy Van Winkle 15. If you want the full picture of how those two lines relate, see our explainer on Weller vs Pappy Van Winkle.
High-rye and low-rye bourbon: corn and spice
Keep wheat out and use rye as the secondary grain and you get a "rye-recipe" bourbon, which most bourbon is. How much rye sets the tone. A low-rye bourbon keeps rye modest, roughly 10% or less, for a softer, more corn-forward style. A high-rye bourbon pushes rye up, generally into the 20% to 35% band while corn still stays above 51%, for a bolder, spicier, more peppery and herbal profile.
A clean real-world reference comes from Buffalo Trace, whose recipes are not officially published but are widely reported by writers like Whisky Advocate. Their Mash Bill #1 is the low-rye recipe (estimated around 10% rye or less) behind the flagship Buffalo Trace and Eagle Rare 10. Their Mash Bill #2 is the higher-rye recipe (estimated around 12% to 15% rye) behind Blanton's, which tastes noticeably spicier. Even within one distillery, shifting the rye a few points moves the glass, which is exactly why collectors track mash bill at all. Worth saying plainly: those Buffalo Trace numbers are well-sourced estimates, not distillery figures, and "high-rye" is relative; Mash Bill #2 is high for Buffalo Trace but still below the 20% to 35% a true high-rye bourbon implies.
Bourbon vs rye whiskey: same barrels, different lead grain
Cross the line entirely, past 51% rye, and you are no longer drinking bourbon. Rye whiskey is the mirror image: rye leads, corn supports, and the spirit comes out drier, grassier, and spicier, with the baking-spice and herbal notes that make rye a cocktail favorite. Same new charred oak, same craft, opposite lead grain. That single swap, from 51% corn to 51% rye, is the cleanest illustration of why the mash bill is the first thing to read on any whiskey.
How to shop by mash bill
Once you can read a mash bill, you can shop by it instead of by hype. A few rules of thumb:
- Want soft, sweet, easy sipping? Look for wheated on the label or a high corn percentage with wheat second.
- Want pepper, structure, and spice? Look for high-rye bourbon, or step over to rye whiskey for the full effect.
- Want a crowd-pleasing middle? A standard or low-rye bourbon sits in the sweet, balanced center.
Mash bill is the best starting point, not the whole story. Yeast, fermentation, proof, barrel char, and years in oak all push the final flavor around. A high-rye is not always hot, and a wheated bourbon is not always soft. Read the recipe first, then trust your own palate.
Record the recipe, then browse your shelf by it
Here is the practical problem: most whiskey apps and spreadsheets drop the mash bill entirely. They will store proof and price, but not the one field that actually predicts taste. So you cannot answer a simple question like "how many wheated bourbons are actually on my shelf?" without opening every bottle's page yourself.
Drambook ships every catalog bottle with its mash bill pre-filled, and lets you tag custom bottles with their grain recipe too, so your shelf becomes searchable by recipe rather than just by name. Add Buffalo Trace and it arrives labeled low-rye, Mash Bill #1; add a Weller and it lands in the wheated group automatically. You can finally browse your collection the way you actually think about whiskey: by what is in the glass. It is the same instinct behind keeping proof and ABV straight (proof vs ABV) and the reason a real catalog beats a spreadsheet once a collection grows (how to catalog a whiskey collection).
Frequently asked questions
What is a mash bill in bourbon?
A mash bill is the recipe of grains used to make a whiskey, given as percentages by weight. In bourbon the mash bill must be at least 51% corn; the rest is usually rye or wheat plus a little malted barley. The mix decides both what the whiskey is legally called and how it tastes.
What percentage of corn makes a bourbon?
At least 51% corn. Under the U.S. standards of identity (27 CFR Part 5), bourbon must be made from a fermented mash of not less than 51% corn. Most bourbons run higher than the minimum, often 65% to 80% corn.
What is a wheated bourbon?
A wheated bourbon uses wheat instead of rye as its secondary grain. It still clears the 51% corn minimum, but wheat in the second slot makes the whiskey softer and sweeter, with honey and bread notes rather than rye's pepper. W.L. Weller and Pappy Van Winkle are the best-known examples.
What does high-rye bourbon mean?
High-rye bourbon has an unusually large share of rye in the mash bill, generally about 20% to 35%, while corn still stays above 51%. The extra rye pushes the flavor toward pepper, baking spice, and herbal notes. It is not the same as rye whiskey, which must be at least 51% rye.
What is the difference between bourbon and rye whiskey?
The mash bill. Bourbon must be at least 51% corn, which makes it sweeter and rounder. Rye whiskey must be at least 51% rye, which makes it drier and spicier. Both age in new charred oak, so the lead grain is the main difference in style.