What Grain Is Bourbon Made From?
Bourbon is made primarily from corn, which must make up at least 51% of the grain mixture by federal law. The remaining grains — most commonly rye, wheat, and malted barley — are called flavor grains, and the specific combination a distillery chooses is called the mash bill. That mash bill is one of the most consequential decisions in bourbon production, because the character it creates cannot be fundamentally changed by any step that follows.
The Four Grains and What Each One Does
Every bourbon mash bill is built from some combination of four grains. Understanding what each one contributes makes it possible to predict how a bourbon will taste before you ever open the bottle.
Corn is the primary grain and the legal minimum is 51%, though most Kentucky distilleries use 65 to 75%. Corn ferments naturally into a full-bodied, sweet spirit. It contributes honey, butterscotch, and caramel character and provides the weight and body that makes bourbon feel substantial in the glass. Without corn, you do not have bourbon.
Rye is the most common secondary grain and appears in the majority of Kentucky bourbons. It produces dryness, spice, and pepper. Rye cuts through corn’s sweetness and adds complexity and a longer, more assertive finish. A rye-heavy mash bill — anything above 20% is considered high-rye — produces a sharper, more angular bourbon. Standard rye content runs 12 to 15%.
Wheat replaces rye as the secondary grain in what are called wheated bourbons. Wheat produces a softer, rounder, more delicate character with less spice and more subtle sweetness. Wheated bourbons tend to be more immediately approachable and age particularly gracefully over long periods. Maker’s Mark, Pappy Van Winkle, and W.L. Weller are all made from wheated mash bills.
Malted barley is present in virtually every bourbon mash bill regardless of style, typically at 5 to 15%. Its primary role is enzymatic: malting the barley produces the amylase enzymes that convert the other grains’ starches into fermentable sugars. Without malted barley, saccharification fails and fermentation efficiency collapses. Malted barley also contributes its own subtle flavor — nutty, biscuity, and slightly earthy notes that add background depth.
Why the Mash Bill Matters So Much
The mash bill is the first and most permanent flavor decision a distillery makes. Under 27 CFR § 5.143, the legal requirements establish minimums and process rules, but within those parameters distilleries have enormous latitude. The mash bill is where that latitude is exercised.
Distillation can concentrate and refine the grain’s character. Barrel aging can add vanilla, caramel, and oak. But neither step can add spice that was never there, or soften a rye-forward profile into a wheated one. The skeletal structure of the bourbon’s flavor — whether it will be sweet or dry, soft or assertive, light or full-bodied — is set in the grain recipe before any water is heated.
This is why two bourbons can come from the same distillery, be aged in identical barrels for the same length of time, and taste noticeably different simply because one uses rye and the other uses wheat as the secondary grain.
Rye-Forward vs. Wheated: The Two Main Styles
Most bourbons fall into one of two broad style categories defined entirely by the secondary grain choice.
Rye-forward bourbons use rye as the secondary grain at anywhere from 10 to 35% of the mash bill. The result is the classic Kentucky profile most people associate with bourbon: sweet corn character undercut by dry, peppery spice, with a finish that tends to linger and build. Buffalo Trace, Bulleit, Four Roses, Wild Turkey, and Jim Beam are all rye-forward bourbons.
Wheated bourbons swap rye for wheat. The spice disappears, replaced by a softer, more delicate sweetness with a shorter, cleaner finish. These bourbons are often described as approachable, round, and easy to drink neat. They also tend to develop more complexity over extended aging because they lack the assertive spice that can become aggressive in very old rye-forward bourbons.
There is no objectively superior style. The preference depends entirely on what the drinker values. Tasting them side by side is the most efficient way to understand the difference.
High-Rye Bourbon: What It Means and Why It Matters
Within the rye-forward category, a distinction has emerged around what are called high-rye bourbons — expressions where rye makes up 20% or more of the mash bill, and sometimes considerably more. High-rye bourbons tend to be drier, sharper, more aromatic, and more complex. They often require a little more patience from new drinkers but reward experienced palates with significant depth.
Some distilleries have built their entire identity around high-rye mash bills. Bulleit Bourbon uses approximately 28% rye, producing the dry, spicy profile that distinguishes it from the softer, more rounded bourbons made at comparable price points.
The Mash Bill at the Distillery
When you visit a Kentucky distillery, the mash bill is one of the first things a knowledgeable guide will explain, because it frames everything else on the tour. Understanding why the distillery chose its specific grain ratios makes the fermenters, the stills, and the tasting room all more legible.
Kentucky produces roughly 95% of the world’s bourbon. The state’s abundance of corn, its limestone-filtered water, and its tradition of distilling craft mean that nearly every iconic mash bill in the category was developed and refined in Kentucky. When you taste the difference between a wheated and a rye-forward bourbon on a tour, you are tasting the direct result of a grain decision made decades or generations ago by a master distiller in a Kentucky grain room.
That grain decision is still being made today, batch by batch, in the same way it has always been made — by choosing which grains, in what ratio, will define this particular bourbon’s character before it ever touches a still or a barrel.
About the Author
Joey Myers
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