barrel (US) [bbl (US)] Unit Converter

Definition of barrel (US) [bbl (US)] unit

A barrel (US) is a customary unit of volume equal to 31.5 US liquid gallons, or approximately 119.24 liters. It is a general US liquid measure and should be distinguished from the 42-gallon petroleum barrel.

History of barrel (US) [bbl (US)] unit

The American barrel developed from European barrel traditions, in which wooden casks served as practical containers and measures for trade. Unlike a standardized modern unit, its size historically varied according to commodity, region, and regulation. In the United States, separate definitions emerged for liquids, dry goods, and petroleum. The US liquid barrel was commonly fixed at 31.5 gallons, while the petroleum industry adopted a 42-gallon standard during the nineteenth century. Consequently, “barrel” remains context-dependent, reflecting commercial practices rather than one universal historical capacity.

Applications of barrel (US) [bbl (US)] unit

Today, the 31.5-gallon US barrel appears mainly in specialized liquid-measure references, historical records, and conversion tools. It may describe quantities of beer, molasses, vinegar, or other commodities when a traditional US measure is intended. In energy markets, however, crude oil is reported in the separate 42-gallon petroleum barrel, so context is essential.

Complete list of barrel (US) [bbl (US)] unit conversion