Barrel (unit)

A barrel is one of several units of volume applied in various contexts; there are dry barrels, fluid barrels (such as the UK beer barrel and US beer barrel), oil barrels and so on. For historical reasons the volumes of some barrel units are roughly double the volumes of others; volumes in common usage range from about 100 litres (22 imp gal; 26 US gal) to 200 litres (44 imp gal; 53 US gal). In many connections the term "drum" is used almost interchangeably with "barrel".