kilderkin

A kilderkin is a traditional unit of volume used in the British imperial system, notably in brewing and the shipping of beer and ale. It denotes 18 imperial gallons, which is about 81.8 liters. The kilderkin is equal to two firkins, with a firkin defined as 9 imperial gallons (roughly 40.9 liters). In the historic cask system, it sits between the smaller firkin and larger measures such as the hogshead and tun used in trade and storage.

The term is thought to derive from a continental source, commonly linked to Dutch keilderken, reflecting linguistic and trade influences on English coopering and commerce. While the exact origin is not definitively established, the word entered English usage in the early modern period.

Historically, kilderkins were used by brewers and merchants to quantify shipments and inventory of beer and other liquids. Today, the unit is largely of historical or ceremonial interest; modern brewers and suppliers typically use metric volumes or widely standardized cask sizes, though some vintage or tradition-focused operations may still reference kilderkins in keeping with historic practice.