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What is a Barrel? Different Barrel Types Explained
A barrel is a unit of volume used for various commodities including oil, beer, wine, and other liquids. However, not all barrels are equal — the volume depends on what’s being measured and which country’s standards apply.
This converter handles 5 different barrel types and 12 common volume units, making it easy to switch between oil industry standards, brewing measurements, and everyday volume units like gallons and liters.
Barrel Conversion Formulas
Conversion between any two units uses these base relationships. All barrel types are first converted to US gallons, then to the target unit.
How to Use This Barrel Converter
- 1Enter your value — the number you want to convert.
- 2Select “From” unit — choose the barrel type or volume unit you’re converting from.
- 3Select “To” unit — choose the target barrel type or volume unit.
- 4Adjust decimal places — control the precision of your result.
- 5Read the result — instant conversion with explanation and quick reference grid.
Worked Example
An oil trader has 500 oil barrels (bbl) and needs to know how many liters that represents:
Barrel Type Comparison Table
| Barrel Type | US Gallons | Liters | UK Gallons | Common Use |
|---|---|---|---|---|
| Oil Barrel (bbl) | 42 | 158.987 | 34.97 | Crude oil, petroleum |
| Beer Barrel | 31 | 117.348 | 25.81 | US brewing industry |
| UK Barrel | 43.23 | 163.659 | 36 | UK beer, ale |
| Federal Barrel | 31.5 | 119.240 | 26.22 | US federal regulations |
| Proof Barrel | 40 | 151.416 | 33.31 | Alcoholic spirits |
Note: The oil barrel is the standard for global petroleum trading. Beer barrels are used in US brewing. UK barrels are imperial measure.
When to Use This Barrel Converter
Convert crude oil production volumes between barrels, gallons, and metric units.
Convert between beer barrels, gallons, and liters for production planning.
Calculate container volumes and liquid cargo quantities.
Convert industrial liquid volumes between different measurement systems.
Convert between US and UK gallon-based barrel systems for global trade.
Convert raw material volumes from barrel shipments to production units.
Frequently Asked Questions
Different barrel sizes evolved historically for different commodities. The oil barrel (42 gallons) became standard in the Pennsylvania oil fields of the 1860s. Beer barrels (31 gallons) reflect traditional US brewing standards. UK barrels (36 imperial gallons) are part of the British imperial system. Each industry developed its own standard based on practical needs, and those standards persist today.
One oil barrel (bbl) equals exactly 158.987294928 liters (approximately 159 liters). This is derived from 42 US gallons × 3.785411784 liters per gallon. This standard is used globally for crude oil trading, though actual tanker volumes may vary slightly due to temperature and other factors.
A US gallon is 3.78541 liters, while a UK (imperial) gallon is 4.54609 liters — about 20% larger. This difference affects barrel conversions significantly. An oil barrel (42 US gal) equals about 35 UK gallons. When converting between barrel types and UK gallons, always verify which gallon standard applies.
Yes, the 42-gallon oil barrel is the standard unit for measuring crude oil and many refined products globally. However, actual shipping containers vary — tanker trucks may hold 50-100 barrels, rail cars 200-400 barrels, and ocean tankers millions of barrels. The barrel is a unit of volume, not a physical container, in modern trading.
Converting barrels to metric tons depends on the density (specific gravity) of the liquid. For crude oil, a common conversion is 1 barrel ≈ 0.136 metric tons (or 1 metric ton ≈ 7.33 barrels). However, different crude grades have different densities. Light crude may be 1 bbl = 0.13 tons, while heavy crude may be 1 bbl = 0.15 tons. For precise conversions, you need the API gravity of the specific oil.
The 42-gallon oil barrel originated in the 1860s in Pennsylvania. Before standardizing, oil was shipped in various containers — whiskey barrels (40 gallons), fish barrels, and molasses barrels (35-40 gallons). The 42-gallon standard was adopted because it was the capacity of a standard wooden barrel used by many Pennsylvania oil producers, and it was convenient for shipping by railroad and wagon.