Barrel (unit)

• A barrel of crude oil (abbreviated bbl) is 42 US gallons, approximately 159 litres. The size originates from the use of 190 litre wine barrels in the early Pennsylvania oil fields, but only counting 160 litres to account for spillage during shipment. Later barrels were only filled to 160 litres. Outside the US, oil is measured by weight in tonnes rather than volume.
• In the UK, a standard beer barrel is 36 UK gallons, about 164 litres.
• In the US, a standard beer barrel is 31.5 US gallons, about 119 litres.