legal
Cask strength
Whisky bottled at or very near the strength at which it came out of the cask, without reduction to a standard bottling strength.
Where it is defined
United States only: 27 CFR 5.87(a) — bottling proof must be no more than two degrees below the proof when dumped from the barrels. NOT defined in the Scotch Whisky Regulations 2009 or Regulation (EU) 2019/787.
Often confused with original or entry proof
27 CFR 5.87(b) reserves 'original proof', 'original cask strength' and 'entry proof' for spirits where barrel-entry proof and bottled proof are identical — a much stronger claim.
Worth knowing
The clearest UK/US asymmetry in this glossary: a Scotch labelled 'cask strength' is making an unregulated marketing claim in its home market, while the same words on a US whiskey carry a two-degree tolerance enforceable by TTB.
Related terms
Last reviewed 2026-07-30 · All glossary terms