What are ‘Cask Strength,’ ‘Barrel Proof,’ and ‘Barrel Strength?’

Is there a difference?

Barrel Proof, Barrel Strength, and Cask Strength

Cask Strength, Barrel Proof, and Barrel Strength are different phrases which mean the same thing… the alcohol-by-volume (ABV) strength or proof is essentially the same as when it came out of the barrel at the time of bottling (as opposed to Full Proof which is the ABV when it went into the barrel). The official rule is that it cannot be more than 1% (2 proof points) lower than when the whiskey was poured from the barrel. Distillers will choose one phrase over the other simply based upon marketing reasons or distillery preferences. The typical level of alcohol-by-volume (ABV) for a barrel proof whiskey is usually in the range of 52–66% ABV (104 – 132 proof), but can be higher.


In 1979, the Federal Bureau of Alcohol, Tobacco, and Firearms “recognized the need to establish guidelines for use of the terms Original Proof, Original Barrel Proof, Entry Proof and Barrel Proof on distilled spirits labels.” (See ATF Ruling 79-9) Original prooforiginal barrel proof, full proof, and entry proof on a label indicate the same thing: “that the proof of the spirits entered into the barrel and the proof of the bottled spirits are the same.” This means that whiskeys with these phrases on their labels must be at the same ABV (proof) as when the whiskey was put into the barrel.

Barrel ProofCask Proof, and Barrel Strength are the proof at when the whiskey leaves the barrel. The rule for these phrases according to ATF Ruling 79-9 is, “the bottling proof is not more than two degrees lower than the proof established at the time the spirits were gauged for tax determination.” Whiskeys are gauged for tax determination when the barrels are dumped for bottling. The ‘2 degrees’ rule gives distillers some wiggle room in case there is a slight proof drop between gauging and bottling. The intention is for the proof in the bottle to match that of the barrel. This is why barrel proof whiskeys will often have an ABV number like 52.7% alcohol rather than a nice round 53%. Generally speaking, Barrel Strength and Barrel Proof are an American phrase while Cask Strength originates (but is not limited to) Scotland, because they call their barrels “casks”.


Because high-proof whiskeys pack a palatable punch of flavors. They have had years in the barrel, seeping into and out of the wood grain, gaining and intensifying flavors as seasons and temperatures change. This is what develops the intense, robust flavors that whiskey and bourbon enthusiasts crave.

Most other whiskeys on the other hand, have water added to them when they come out of the barrel. This is to make them less expensive and to make them appeal to a broader range of palates who do not enjoy a high-proof spirit. Most whiskey in the US have enough water added to make them 40% ABV (80 proof), which is the lowest legal limit to be called whiskey in the US.

Adding water to the whiskey greatly reduces its flavor and character. Whiskey & bourbon connoisseurs prefer the higher proof because it typically (but not always) means more flavor and a better whiskey.

Denny Potter, former Heaven Hill Master Distiller said, “We produce barrel proof whiskey because whiskey connoisseurs demand it. The desire to chart your own course with barrel-proof whiskeys is undeniable. Whether you want the straight-out-of-the-barrel robustness or controlled dilution, someone can find their perfect sip. But knowing a barrel proof bourbon’s provenance contributes here as well. We often make it clear where single barrels or many of our batches come from. And to understand the variances of aging on proof and flavor most effectively comes out in barrel proof whiskeys.”

One common misconception about barrel proof whiskeys is that you are supposed to drink them straight. You certainly can if you wish, or you can adjust the proof by adding water to suit your personal preference.

“Dad always told everyone to add some water or ice to the Booker’s bourbon to open it up and enjoy it at the strength you enjoy it,” says Fred Noe, Jim Beam Master Distiller and Booker’s son. “I practice that myself and I add some ice and water to Booker’s.”


Barrell Cask-Strength bourbon (Batch 23)

Maker’s Mark Cask Strength Kentucky straight bourbon (Batch 19-01)

Knob Creek Cask-Strength rye

Stagg Jr. Barrel Proof Kentucky straight bourbon (13th Edition)

Elijah Craig Barrel Proof Kentucky straight bourbon (Batch A120)

Jack Daniel’s Single Barrel Special Release Coy Hill High Proof

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