Barrel

A barrel is the standard volume unit for crude oil and refined products, equal to 42 US gallons, used in pricing and production statistics worldwide.

A barrel is the standard unit for measuring and pricing crude oil and refined petroleum products, equal to 42 US gallons, a figure that dates back to the size of wooden barrels used to transport oil in the earliest days of the American oil industry. It has stayed the standard ever since, long after oil stopped moving in actual wooden barrels.

Nearly every crude oil price quoted anywhere in the world, from Dated Brent to WTI, is expressed in dollars per barrel, and production and consumption statistics for oil are typically reported in barrels or barrels per day. Refined products such as gasoline and diesel are also commonly measured in barrels, even though retail fuel is sold to consumers in smaller units like gallons or liters.