Barrel (oil, bbl)
The oil barrel, symbol bbl, is a unit of volume commonly used in the petroleum industry. Its origins date back to the mid-19th century, when the American oil industry adopted the wooden barrel as a standard for storage and transportation. In 1866, the barrel was officially set at 42 US gallons (about 159 liters) to unify trade and pricing. Although physical barrels are no longer used, the “barrel” remains a widely recognized standard for oil production, consumption, and trading. The oil barrel is commonly referenced in discussions of energy, economics, and industrial development as a non-metric unit of volume.
Liter (L)
The liter, symbol L, is a metric unit of volume equal to one cubic decimeter (dm³). First introduced in France in 1795, it became the standard for everyday liquid measurements. While technically not a SI base unit, the liter is accepted for use with the SI due to its practicality. One liter equals 1,000 milliliters and 0.001 cubic meters, and is used worldwide as a unit of volume. It is utilized in cooking, chemistry, and other applications where standard volume measurement is required.