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
Barrel of the same volume as five US bushels. However, by 1866, the oil barrel was standardized at 42 US gallons. Oil has not been shipped in barrels since the introduction of oil tankers, but the 42 US gallon size is still used as a unit for measurement, pricing, and in tax and regulatory codes. Each barrel is refined into about of gasoline, the rest becoming other products such as jet fuel and heating oil, using fractional distillation. Barrels have a convex shape and bulge at their center, called bilge. This facilitates rolling a well-built wooden barrel on its side and