Barrel (unit) continued to use the same size barrels. In the worldwide oil industry, an oil barrel is defined as 42 US gallons, which is about litres or 35 imperial gallons. Oil companies that are listed on American stock exchanges typically report their production in terms of volume and use the units of bbl, Mbbl (one thousand barrels), or MMbbl (one million barrels) and occasionally for widest comprehensive statistics the Gbbl (or sometimes Gbl) denoting a billion. There is a conflict concerning the units for oil barrels (see ). For all other physical quantities, according to the International System of Units, the
Cubic mile of oil of oil (1.26 trillion U.S. gallons or 4.75 trillion litres) each year. Numbers of this magnitude are difficult to conceive by most people. The volume occupied by one trillion U.S. gallons is about one cubic mile. Crane felt that a cubic mile would be an easier concept for the general public than a trillion gallons. The CMO is the energy released by burning a cubic mile of oil. Conversions to other units may be calculated based on the barrel of oil equivalent (BOE), an approximation of the energy released by burning one 42-US-gallon barrel of crude oil. Since one BOE