Barrel

A barrel (symbol: bbl) is a standard unit of volume widely used in the global energy industry to measure crude oil and petroleum products. Defined specifically as 42 United States gallons, one oil barrel equals approximately 158.987 liters or 0.158987 cubic meters. The 42-gallon standard originated in the Pennsylvania oil fields during the 1860s, where wooden tight barrels were standardized to ensure buyers received a full measure despite transport leakage.