From
bblBarrel
The oil barrel equals 158.987 litres or 42 US gallons. It is the global pricing unit for crude oil and petroleum products. The US dry barrel (115.6 L) and UK beer barrel (163.7 L) are different units that share the same name.
Real-world: Brent crude and WTI oil are priced in US dollars per barrel. Global oil demand is about 100 million barrels per day.
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