Barrel

The reference cask of the British brewing trade, holding 36 imperial gallons and anchoring the entire cask hierarchy.

Every traditional brewery cask is defined as a fraction or multiple of the barrel: a firkin is a quarter, a kilderkin a half, and a hogshead one and a half. Standardised under the Weights and Measures Act of 1824 alongside the imperial gallon, the barrel remains the unit in which British breweries still report their annual production output.