Oil Barrels to US gallons
1 bbl = 42 US gal, derived from exact unit definitions.
| bbl | US gal |
|---|---|
| 1 bbl | 42.0 US gal |
| 2 bbl | 84.0 US gal |
| 5 bbl | 210.0 US gal |
| 10 bbl | 420.0 US gal |
| 25 bbl | 1,050.0 US gal |
| 50 bbl | 2,100.0 US gal |
| 100 bbl | 4,200.0 US gal |
US gallons = oil barrels × 42Exact, and an integer. The petroleum barrel is defined as 42 US gallons in US federal regulation and in every API measurement standard.How to convert oil barrels to US gallons
Multiply by 42. The only real difficulty with this conversion is making sure the word “barrel” means what you think it means — it is the most overloaded unit in common use.
- Confirm it is a petroleum barrel (bbl). It is 42 US gallons.
- Multiply by 42.
- Check the magnitude: gallons should be about forty times the barrel figure.
| Which barrel | US gallons | Litres |
|---|---|---|
| Petroleum barrel (bbl) | 42 | 158.99 |
| US beer barrel | 31 | 117.35 |
| US dry barrel | ≈ 26.25 | ≈ 115.6 |
| “Drum” (often miscalled a barrel) | 55 | ≈ 208 |
The 55-gallon drum confusion is the expensive one. A drum is not a barrel, and reading a drum count as barrels overstates volume by 31 %.
A 500-barrel field storage tank
- 500 × 42 = 21,000 US gal
- Also 500 × 158.987294928 = 79,494 L
- Also 21,000 × 0.1336805556 = 2,807 ft³
500 bbl = 21,000 US gallons
Oilfield tanks are specified in barrels — 210, 300, 400 and 500 bbl are the common sizes — so the barrel figure is usually the authoritative one and the gallon figure is the derived one.
A 210-barrel tank battery vessel
- 210 × 42 = 8,820 US gal
- Gauged at 6 ft 3 in of 15 ft 6 in shell height
- Only the tank's own strapping table converts that height to volume
210 bbl = 8,820 US gallons full
Daily production, into gallons
- Reported: 1,250 bbl/day
- 1250 × 42 = 52,500 gal/day
- 52,500 ÷ 1,440 = 36.5 gal/min average
1,250 bbl/d = 52,500 US gal/d
Where the 42 comes from
Not from physics. The 42-gallon barrel was adopted by Pennsylvania oil producers in the 1860s, borrowing the size of the English tierce used for wine and fish, because it was the largest cask two men could reliably roll and it survived transport with about 40 gallons intact. The industry standardised on it, and it has since been written into federal regulation.
43 CFR § 3174.2 “Barrel (bbl) means 42 standard
United States gallons.”
Base conditions: 60 °F, 14.696 psia
NIST SP 811 B.8 barrel [for petroleum, 42 gallons (U.S.)]
→ 1.589 873 E+02 L
1 bbl = 42 × 3.785411784 = 158.987294928 L exactlyFAQ
How many gallons are in a barrel of oil?
Exactly 42 US gallons. The figure is fixed in US federal regulation — 43 CFR § 3174.2 defines a barrel as 42 standard United States gallons — and is used throughout API measurement standards and EIA statistics.
Is a 55-gallon drum a barrel?
No, and the confusion is costly. A drum is 55 US gallons (about 208 litres); a petroleum barrel is 42 US gallons. Treating drums as barrels overstates volume by 31 %.
How many litres in a barrel?
158.987294928 L exactly, since 42 × 3.785411784 = 158.987294928. Commonly quoted as 159 litres.
Why 42 gallons?
Historical accident. 1860s Pennsylvania producers adopted the 42-gallon tierce cask because it was the largest size two men could handle and it arrived with roughly 40 gallons still in it. The convention stuck and was later codified.
Does a barrel change with temperature?
The unit does not; the oil does. Trade is done in standard barrels referred to 60 °F, so an observed volume must be corrected before it becomes a traded quantity.
Sources and standards
Every factor on this page is traced to the document that defines it. Where a value is exact, it is exact because the cited standard makes it so — not because we rounded it well.
- 43 CFR Part 3170, Subpart 3174 — Measurement of Oil (§ 3174.2, Definitions)U.S. Bureau of Land Management, via the electronic Code of Federal Regulationshttps://www.ecfr.gov/current/title-43/subtitle-B/chapter-II/subchapter-C/part-3170/subpart-3174Binding federal regulation for oil measurement on federal and Indian leases. Defines a barrel as 42 standard U.S. gallons and sets the base conditions those gallons are referred to: 60 °F and 14.696 psia.
- Energy Glossary — “Barrel”U.S. Energy Information Administrationhttps://www.eia.gov/tools/glossary/index.php?id=bThe U.S. federal energy statistics agency defines the barrel as a unit of volume equal to 42 U.S. gallons. All EIA production, refining and stock series are published on this basis.
- Special Publication 811, Appendix B.8 — Factors for Units Listed AlphabeticallyNational Institute of Standards and Technologyhttps://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8NIST's master table of conversions into SI. Factors printed in boldface are exact by definition rather than measured or rounded — which is how you tell a defined unit from an approximated one.
- Manual of Petroleum Measurement Standards (MPMS) — Ch. 1 “Vocabulary”, Ch. 11.1 “Temperature and Pressure Correction Factors”, Ch. 12.1 “Calculation of Static Petroleum Quantities”American Petroleum Institute (with ASTM D1250 / ISO 91 volume correction tables)Paid standard — cited by designation; obtain from the publisher.The industry standard for turning a gauged tank volume into a traded quantity: observed volume, gross standard volume at 60 °F, and net standard volume after sediment and water. A unit conversion is only the first step of that chain.
- Handbook 44, Appendix C — General Tables of Units of MeasurementNational Institute of Standards and Technology, U.S. Department of Commercehttps://www.nist.gov/document/2026-nist-handbook-44-appendix-cThe legal-metrology reference for U.S. customary units. Fixes the U.S. liquid gallon at exactly 231 cubic inches and tabulates the full liquid-volume chain (minim → fluid dram → fluid ounce → gill → pint → quart → gallon).
Every linked source above was retrieved and checked on 2026-09-02. Factors quoted as exact are exact by definition in the cited document, not rounded by us.