English brewery cask units
Capacities of brewery casks were formerly measured and standardised according to a specific system of English units. The system was originally based on the ale gallon of 282 cubic inches. In United Kingdom and its colonies with the adoption of the imperial system in 1824, the units were redefined in terms of the slightly smaller imperial gallon. The older units continued in use in the United States.
Historically the terms beer and ale referred to distinct brews. From the mid 15th century until 1803 in Britain "ale" casks and "beer" casks differed in the number of gallons they contained.
The tun is a cask that is double the size of a butt and is equal to six barrels and has a capacity of 216 imperial gallons (982.0 l). Invented in Brentford, a tun was used in local breweries to measure large amounts alcohol.
The butt of beer was equal to half a tun, two hogsheads, three barrels or 108 imperial gallons (491.0 l).
The hogshead of beer and ale was equal to a quarter of a tun, half a butt, a barrel and a half or three kilderkins. This unit is close in size to the wine hogshead.
The barrel of beer or ale was equal to two kilderkins or 2⁄3 of a beer or ale hogshead. This is somewhat larger than the wine barrel.
The kilderkin (from the Dutch for "small cask") is equal to half a barrel or two firkins.
The kilderkin is still currently used. It is the unit of choice of CAMRA, the Campaign for Real Ale CAMRA for calculating beer quantities for beer festivals in the UK. Ales are usually delivered in firkins, cider and other drinks are usually in boxes, bottles or other containers measured in gallons or litres, and all (except wine) are sold in pints or parts thereof. For CAMRA internal accounting, all are calculated in kilderkins. A kilderkin is 144 pints.
The ale or beer firkin (from Middle Dutch vierdekijn meaning "fourth") is a quarter of an ale or beer barrel or half a kilderkin. This unit is much smaller than the wine firkin. Casks in this size (themselves called firkins) are the most common container for cask ale.
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