A standard oil barrel holds 42 gallons or approximately 159 litres of crude oil. Using the industry standard "barrel of oil equivalent" (BOE), a barrel of crude oil is said to be equal to 6,000 cubic feet of natural gas with an energy equivalent of 1,700 kilowatt hours.
The standard 42-gallon barrel, which had been carefully crafted and used to ship dry goods for hundreds of years, was made watertight and adopted for use in the petroleum industry in 1872. A full barrel carries enough oil to make shipping profitable, and weighs in at the top end of what could be physically managed by the men moving them.
