Barrels to Gallons Converter
Instantly convert barrels to gallons (US & UK). Our tool clarifies the difference and converts for Oil barrels (bbl), liquid barrels, beer barrels, and dry barrels.
Conversion Inputs
Edit either field; the calculator keeps the alternative value in sync. Use the barrel selector to switch between the different historical barrel sizes.
How to Use This Converter
Choose the barrel variant that matches the industry you are referencing, then enter either barrels or gallons. Click "Calculate" or wait for the inputs to update to see the counterpart value. The calculator always keeps both fields synchronized with a consistent conversion factor.
Understanding the Barrel Variants
Unlike standardized units such as meters or kilograms, a "barrel" can hold different volumes depending on the commodity. The default US Oil Barrel (bbl) is 42 US gallons, but there are other definitions for liquid chemicals, beer, dry goods, and the British Imperial system.
Conversion Factors Used
- 1 US Oil Barrel (bbl) = 42 US Gallons
This is the standard for measuring crude oil and other petroleum products. - 1 US Liquid Barrel = 31.5 US Gallons
Used for a few liquid commodities such as chemicals or food products. - 1 US Beer Barrel = 31 US Gallons
This volume is legally defined in the United States for taxation on beer production. - 1 US Dry Barrel = 28.37759 US Gallons
Equivalent to 105 dry quarts, commonly used for dry commodities. - 1 UK (Imperial) Barrel = 43.23405 US Gallons
Based on 36 Imperial gallons, the UK unit is bigger than the US gallon.
Conversion Table (Oil Barrels)
The following table highlights the most common US Oil Barrel conversions so you can see the scaling factor at a glance.
| US Oil Barrels (bbl) | US Gallons |
|---|---|
| 1 bbl | 42 gal |
| 2 bbl | 84 gal |
| 5 bbl | 210 gal |
| 10 bbl | 420 gal |
| 50 bbl | 2,100 gal |
| 100 bbl | 4,200 gal |
Frequently Asked Questions (FAQ)
How many gallons are in a barrel of oil?
One standard US Oil Barrel equals exactly 42 US gallons. This is the default used by international crude oil markets.
How many gallons are in a barrel of beer?
A US beer barrel is defined by federal law as 31 US gallons; a keg is often a half-barrel (15.5 gallons).
Why is an oil barrel 42 gallons?
The 42-gallon size dates back to the 1870s in Pennsylvania, when oil producers repurposed whiskey barrels of that capacity for shipping crude. The size stuck to avoid disputes and create a consistent trading unit.