» See Barrel (disambiguation) for other uses. The barrel is the name of several units of volume: Oil barrel: 42 US gallons, 158.9873 litres, or 34.9723 Imperial (UK) gallons. UK beer barrel: 36 UK gallons (163.7 litres). US beer barrel: 31 US gallons (117.3 litres), the result of tax law definitions. US non-beer liquid barrel: 31½ US gallons (119.2 litres), or half a hogshead. US dry barrel: 105 dry quarts (115.6 litres). Somali water barrel: 200 litres - used in Horn of Africa to… (More on Mbbl)