Updated July 2026.
“Barrel proof” or “cask strength” on a US distilled-spirits label means the bottling proof is not more than two degrees lower than the proof when the spirits were dumped from the barrel (27 CFR 5.87(a)). It is not a fixed number. It is not a synonym for 100 proof or bottled-in-bond. A barrel-proof bourbon might be 108.2 or 131.4 — whatever that barrel or batch registered after aging, minus at most two proof degrees of water.
“Original proof,” “original barrel proof,” “original cask strength,” or “entry proof” is stricter: entry proof and bottled proof must be the same (5.87(b)). Most modern “barrel proof” whiskey entered the barrel at up to 125 proof and came out higher or lower as water moved. See whiskey proof and 100-proof.
Barrel proof vs nearby words
| Term | Legal meaning | Typical pour math |
|---|---|---|
| Barrel proof / cask strength | Bottled within 2 proof degrees of dump proof (5.87(a)) | 1.5 oz at 60% ABV = 1.50 std drinks |
| Original / entry proof | Bottled proof equals entry proof (5.87(b)) | Rare on modern bourbon |
| Bottled-in-bond | Exactly 100 proof + 1897 Act rules | 1.25 drinks / 1.5 oz |
| 100 proof | 50% ABV only | Not automatically barrel proof |
| Cask finish | Second barrel for flavor; no 5.87 proof promise | Use labeled ABV |
Wild Turkey and others describe barrel proof as “no water added.” TTB still allows those two proof degrees. Batch variation is the point. A 1.5-ounce pour of 125-proof whiskey is 1.56 standard drinks. Four such pours are more than six drinks. NIAAA binge pattern is a health line, not a target. Do not drive. Calories scale with ethanol (~7 kcal/g), not with the 97-kcal 80-proof USDA line.
Sources
- 27 CFR 5.87 (e-CFR; reviewed 2026): barrel proof / cask strength; original/entry proof.
- 27 CFR 5.88: bottled in bond (different rule).
- NIAAA standard drink (December 2025).