Gallon Barrel Converter

One barrel is 42 gallons, or 158.99 liters

The barrel (bbl) used for crude oil and petroleum products is exactly 42 US gallons. The US gallon is defined as 231 cubic inches, or 3.785411784 L, so one barrel is 42 × 3.785411784 = 158.987294928 L, usually written 158.99 L or 159 L. That is 0.159 m³, or 34.97 imperial gallons. Going the other way, 1 gallon is 1 ÷ 42 = 0.0238 barrel, and 1 m³ (1 kL) is 6.29 barrels.

The converter above links six fields: oil barrels, US gallons, liters, cubic meters, imperial gallons and tonnes of crude. Type a number into any one of them and the other five update. A field that shows a rounded value gets a "≈" after its label. Below the fields you can see the same volume as beer barrels or 55-gallon drums, find where it falls on a size ladder that runs from 1 L to the world's daily oil use, and turn an oil price per barrel into a price per gallon and per liter.

When you need to convert gallons and barrels

• Reading "barrels per day" in the news: EIA reports and OPEC headlines quote output and demand in barrels, usually per day (bpd or b/d). One million barrels a day is 42 million US gallons, about 159 million liters, and roughly half of what one supertanker carries (about 2 million barrels). In gallons or tanker loads the number is easier to picture.
• Comparing crude with the price at the pump: crude is quoted in dollars per barrel and gasoline in dollars per gallon. Divide the barrel price by 42 and you can set the two side by side and see what share of a gallon of gas is crude.
• Moving a spec sheet or tank size into metric: US equipment specs, tank capacities and permits are often in gallons or barrels. Before you put liters or cubic meters in a report, check that the "barrel" in the source is the 42-gallon oil barrel.
• Matching tonnes with barrels: trade and refining statistics outside the US often come in tonnes, while prices and production are in barrels. A conversion factor such as 7.33 barrels per tonne of crude puts both on one scale.

How to use the converter

1. Type a number into the field for the unit you know. Enter barrels, for example, and the gallons, liters, cubic meters, imperial gallons and tonnes are filled in. The field you typed in last is the one the others follow, and its border turns darker.
2. The answer strip at the top shows the gallon value when you entered barrels and the barrel value when you entered anything else. A "≈" after a label means the value was rounded to the decimals you picked.
3. Choose 0, 2, 4 or 6 decimal places. If a value above zero is so small it would show as 0, the converter shows three significant digits instead.
4. Under "Tonne conversion basis" pick crude oil, gasoline, kerosene, diesel or fuel oil, and the tonne field is recalculated with that product's factor.
5. Tap a picture under "Which barrel are you counting?" to switch the barrel field to the oil barrel (42 US gal), the US liquid barrel (31.5), the US beer barrel (31) or the 55-gallon drum. The number under each picture is how many of that barrel the current volume makes up.
6. In the price box, enter the oil price per barrel in dollars to get the price per gallon, per liter, per imperial gallon and per cubic meter. Add what regular gasoline costs per gallon at your station and a bar shows how much of it is crude.

The math: from 3.785411784 L to 158.987 L

Gallons and barrels are both set by definition, so no approximation creeps into the arithmetic.

1. An inch is exactly 2.54 cm and the US gallon is defined as 231 cubic inches, so 1 US gal = 231 × 16.387064 cm³ = 3.785411784 L.
2. The oil barrel is 42 US gal, so 1 bbl = 42 × 3.785411784 = 158.987294928 L = 0.158987294928 m³.
3. To turn gallons into barrels, divide by 42. To turn barrels into gallons, multiply by 42.
4. To turn liters into barrels, divide by 158.987294928. One cubic meter (= 1 kL = 1,000 L) is 1,000 ÷ 158.987294928 = 6.2898 barrels.
5. The imperial gallon is a separate unit of 4.54609 L, so 1 bbl = 158.987294928 ÷ 4.54609 = 34.97 Imp gal.
6. A tonne is a weight, so it needs a density to become a volume. The converter uses the factor from the KNOC table (1 t of crude = 7.33 bbl), which gives 1 t = 7.33 × 158.987 = 1,165.4 L.

NIST's conversion tables also list the petroleum barrel as 0.158 987 3 m³. If you round to 159 L, a million barrels comes out about 12,705 L too high, so for large numbers it pays to use the defined value.

Common barrel values

Converting gallons and liters to barrels

55 gallons is the capacity of one drum. It equals 1.3095 oil barrels, so a count of drums treated as barrels understates the volume: 100 drums are 130.95 oil barrels, not 100.

Not every barrel is the same: 42, 31.5 and 31 gallons, and the 55-gallon drum

NIST Handbook 44 notes that the barrel is defined differently by law and by industry practice, and tells readers to check the definition that fits their use in the relevant regulations and trade standards. The federal beer tax uses a 31-gallon barrel, many state laws set the "liquid barrel" at 31.5 gallons, federal law recognizes a 40-gallon barrel for distilled spirits, and by long practice crude oil and petroleum products count 42 gallons to the barrel. The federal regulation 27 CFR 25.11 also defines a beer barrel as 31 U.S. gallons.

The 55-gallon drum is not a unit. It is the name for a common size of steel or plastic container. Some people call it a "barrel", but it is 31% larger than the barrel in oil statistics, so when a source gives a quantity in drums, find out which one it means. Tap a picture in the converter and the barrel field switches to that type, so you can see right away how many of it the same volume makes.

Why 42 gallons?

According to the American Oil & Gas Historical Society (AOGHS), early oil producers who met in Titusville, Pennsylvania, in August 1866 agreed that 42 gallons would count as one barrel of oil, and in 1872 the Petroleum Producers Association of that region adopted the standard. Before that, producers shipped oil in containers of different sizes, which made trading and bookkeeping a hassle.

Accounts differ on why the number was 42. AOGHS points out that the 42-gallon "tierce" cask, already a standard container for fish, molasses, whale oil and other goods, held about 300 pounds when filled with oil, a weight a person could handle. Oil no longer travels in wooden casks, but 42 gallons stayed as the unit of statistics and prices. That is why one barrel comes out as the odd-looking 158.99 L.

How many barrels in a tonne of crude?

A tonne is a weight and a barrel is a volume, so you need the oil's density to convert between them. The conversion table that the Korea National Oil Corporation (KNOC) Petronet publishes on Opinet counts 7.33 barrels in a tonne of crude, a value that assumes an average crude density. Lighter crude fills more barrels per tonne, and heavier crude fills fewer.

The last column is the multiplier for turning daily output (barrels per day) into annual weight (tonnes per year). A million barrels of crude a day comes to 1 million × 49.8 = about 49.8 million tonnes a year. The converter's tonne field uses the factor of whichever product you pick under "Tonne conversion basis".

From dollars per barrel to dollars per gallon

Divide the barrel price by 42 and you have the price per gallon. Divide it by 158.987 and you have the price per liter. EIA's West Texas Intermediate (WTI) spot price on October 14, 2026 was $101.91 a barrel, which gives 101.91 ÷ 42 = $2.43 per gallon, or $0.641 per liter.

In the week of October 12, 2026, EIA's U.S. average for regular gasoline was $4.331 a gallon. A gallon of crude at $2.43 is about 56% of that, and the other $1.901 pays for refining, taxes, distribution and margins. A gallon of crude does not become a gallon of gasoline, though, so treat the share as a rough comparison. Enter today's crude price and the price at your own station in the converter's price box to run the same calculation.

What comes out of a barrel of crude

The U.S. Energy Information Administration (EIA) says that U.S. refineries produce, on average, about the following from one 42-gallon barrel of crude oil. Not all of it becomes gasoline, which is worth remembering when you compare crude prices with pump prices.

Distillate is mostly sold as diesel and, in some states, as heating oil. EIA adds that refineries make more than a dozen other products, including the feedstocks the petrochemical industry uses for chemicals and plastics. Yields vary with the refinery and the crude.

Getting a feel for big numbers

The converter's size ladder puts everything from 1 L to the world's daily oil use on a logarithmic scale where each tick is 10 times the last, and marks where your volume falls. The large reference values on it come from EIA.

The rail tank car and unit train figures are the ones EIA used in 2012 when describing crude-by-rail shipments. The supertanker (VLCC) is EIA's 2018 figure for its capacity, and world use is the 2025 value from the October 2026 Short-Term Energy Outlook. Real ships and trains vary in size, so treat these as rough yardsticks.

Common mistakes

• Counting a 55-gallon drum as one barrel: a drum holds 208.2 L, which is 31% more than an oil barrel (158.99 L). One hundred drums are 130.95 oil barrels.
• Mixing beer or liquid barrels with oil barrels: the beer barrel is 31 gallons and the liquid barrel 31.5, so each is 74% to 75% of an oil barrel. The same 100 gallons make 2.38 oil barrels but 3.23 beer barrels.
• Entering imperial gallons as US gallons: an imperial gallon is about 20% bigger than a US gallon. If your source is British, use the imperial gallon field to get the right barrel count.
• Confusing daily output with annual volume: "bpd" and "b/d" mean barrels per day. For a year, multiply by 365: one million barrels a day is 365 million barrels a year.
• Comparing a liter or gallon of crude directly with gasoline prices: the pump price adds refining, taxes and distribution, and a gallon of crude does not turn into a gallon of gasoline. The crude share is only a rough comparison.
• Treating tonnes and barrels as a fixed ratio: 7.33 is the figure for average crude. Gasoline is 8.45 barrels to the tonne and fuel oil 6.70, and every product differs.

Limits and cautions

• This is a calculator that converts volumes by definition. It does not adjust for temperature or for the metering corrections used in real trades.
• The tonne field uses an average conversion factor, which may differ from the actual density of a particular crude. If you need an exact figure, calculate it separately with that crude's density.
• The starting values in the price box (WTI $101.91 a barrel, regular gasoline $4.331 a gallon) are examples dated as above. Check the EIA pages for today's figures and replace them.
• The crude share of the pump price is a simple comparison. It ignores refining yields, tax structure and the lag before crude prices reach the pump.
• The tank car and tanker values on the size ladder are representative approximations.

Basis: unit factors are definitions from NIST and US federal regulations and do not change. Tonne factors come from the KNOC Petronet table on Opinet, refining yields, shipping and consumption figures from EIA, and the crude and gasoline prices from EIA. All were checked on October 20, 2026.

Sources

• 01NIST Guide to the SI — Appendix B.8barrel [for petroleum, 42 gallons (U.S.)] = 0.158 987 3 m³, gallon (U.S.) = 3.785 412 L, gallon (Imperial) = 4.546 09 L
• 02NIST SP 1038 — Conversion Factors for General UseUS gallon = 128 fl oz (231 in³)
• 03NIST Handbook 44 (2026) — Appendix C, General Tables of Units of MeasurementBarrel (liquid) 31 to 42 gal: beer tax 31, many state laws 31½, distilled spirits 40, petroleum 42 (footnote 22)
• 04eCFR — 27 CFR 25.11 Meaning of termsBarrel: 31 U.S. gallons (beer)
• 05U.S. EIA — Glossary: BarrelA unit of volume equal to 42 U.S. gallons
• 06American Oil & Gas Historical Society — History of the 42-Gallon Oil BarrelAugust 1866 Titusville agreement, 1872 Petroleum Producers Association adoption, 42-gallon tierce (updated 2026-01-10)
• 07Opinet — unit conversion table (crude oil conversion)1 t of crude = 7.33 bbl, gasoline 8.45, kerosene 7.80, diesel 7.50, fuel oil 6.70, bbl/day to t/year 49.8 (data from KNOC Petronet)
• 08U.S. EIA — Refining crude oilFrom a 42-gallon barrel of crude: gasoline 19 to 20, distillate 11 to 13, jet fuel 3 to 5 gallons
• 09U.S. EIA — Rail deliveries of oil and petroleum products up 38% in first half of 2012Rail tank car about 700 barrels, unit train up to 85,000 barrels (2012-07-26)
• 10U.S. EIA — U.S. Gulf Coast port limitations impose additional costs on rising U.S. crude oil exportsVLCC about 2 million barrels (2018-05-16)
• 11U.S. EIA — Short-Term Energy Outlook, Global oil marketsWorld petroleum and liquid fuels consumption in 2025: 104.4 million barrels per day (published 2026-10-06)
• 12U.S. EIA — Spot Prices (crude oil, petroleum products)WTI spot $101.91 per barrel (2026-10-14)
• 13U.S. EIA — Gasoline and Diesel Fuel UpdateU.S. regular gasoline $4.331 per gallon (week of 2026-10-12)

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