Barrel (unit)
Encyclopedia
A barrel is one of several units
Units of measurement
A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...

of volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....

, with dry barrels, fluid barrels (UK beer barrel, U.S. beer barrel), oil barrel, etc. The volume of some barrel units is double others, with various volumes in the range of about 100 –.

## Dry goods

• US dry barrel: 7056 cubic inches (115.7 l) (~3.28 bushel
Bushel
A bushel is an imperial and U.S. customary unit of dry volume, equivalent in each of these systems to 4 pecks or 8 gallons. It is used for volumes of dry commodities , most often in agriculture...

).
• Defined as length of stave 28+1/2 in, diameter of head 17+1/8 in, distance between heads 26 in (66 cm), circumference of bulge 64 in (1.6 m) outside measurement; representing as nearly as possible 7,056 cubic inches; and the thickness of staves not greater than 4/10 in ([Ø ≈ 20.37 in (51.7 cm)]). Any barrel that is 7,056 cubic inches is recognized as equivalent.
• US barrel for cranberries 5826 cubic inches (95.5 l) (~2.71 bushel
Bushel
A bushel is an imperial and U.S. customary unit of dry volume, equivalent in each of these systems to 4 pecks or 8 gallons. It is used for volumes of dry commodities , most often in agriculture...

)
• Defined as length of stave 28+1/2 in, diameter of head 16+1/4 in, distance between heads 25+1/4 in, circumference of bulge 58+1/2 in outside measurement; and the thickness of staves not greater than 4/10 in ([Ø ≈18.62 in (47.3 cm)]). No equivalent in cubic inches is given in the statute, but later regulations specify it as 5,826 cubic inches.

Some products have a standard weight or volume that constitutes a barrel:
• cornmeal
Cornmeal
Cornmeal is flour ground from dried maize or American corn. It is a common staple food, and is ground to fine, medium, and coarse consistencies. In the United States, the finely ground cornmeal is also referred to as cornflour. However, the word cornflour denotes cornstarch in recipes from the...

, 200 pounds (90.7 kg)
• Portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...

, 4 cubic feet (113 l) or 376 pounds (170.6 kg). small barrel.

## Fluid barrel

Fluid barrels vary depending on what is being measured and where. For barrels of oil, see the next section.

In the U.K. a beer barrel is 36 imp gal (43 US gal; 164 l). In the U.S. most fluid barrels (apart from oil) are 31.5 US gal (26 imp gal; 119 l) (half a hogshead
A hogshead is a large cask of liquid . More specifically, it refers to a specified volume, measured in either Imperial units or U.S. customary units, primarily applied to alcoholic beverages such as wine, ale, or cider....

), but a beer barrel is 31 US gal (26 imp gal; 117 l).

A keg (of beer) is 15.5 gallons.

## Oil barrel

• Oil barrel, (abbreviation bbl): 42 US gal (34.9723 imp gal; 158.9873 l)(but see caveat below regarding conversion to metric units)

The standard oil barrel of 42 US gallons is used in the United States as a measure of crude oil and other petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

products. Elsewhere, oil is commonly measured in cubic metre
Cubic metre
The cubic metre is the SI derived unit of volume. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère...

s (m3) or in tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

s (t), with tonnes more often being used by European oil companies. International companies listed on American stock exchanges tend to express their oil-production volumes in barrels for global reporting purposes, and those listed on European exchanges tend to express their production in tonnes. There can be 6 to 8 barrels of oil in a ton, depending on density. For example: 256 U.S. gallons [6.1 bbl] of heavy distillate per ton, 272 gallons [6.5 bbl] of crude oil per ton, and 333 gallons [7.9 bbl] of gasoline per ton.
The wooden oil barrel of the late 19th century is different from the modern-day 55-gallon steel drum
Drum (container)
A drum is a cylindrical container used for shipping bulk cargo. Drums can be made of steel, dense paperboard , or plastics, and are generally used for the transportation and storage of liquids and powders. Drums are often certified for shipment of dangerous goods...

(known as the 45-gallon drum in Britain and the 210/200-litre/kg drum elsewhere). The 42-US-gallon oil barrel is a unit of measure, and is no longer used to transport crude oil, as most petroleum is moved in pipelines
Pipeline transport
Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....

or oil tanker
Oil tanker
An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk transport of oil. There are two basic types of oil tankers: the crude tanker and the product tanker. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries...

s.

In the United States, the 42-US-gallon size of barrel as a unit of measure is largely confined to the oil industry, while different sizes of barrel are used in other industries. Nearly all other countries use the metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...

. Many oil-producing countries use the American oil barrel.

The measurement originated in the early Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

oil field
Oil field
An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...

s. In the early 1860s, when oil production began, there was no standard container for oil, so oil and petroleum products were stored and transported in barrels of different shapes and sizes. Some of these barrels would originally have been used for other products, such as beer, fish, molasses or turpentine. Both the 42-US-gallon
Gallon
The gallon is a measure of volume. Historically it has had many different definitions, but there are three definitions in current use: the imperial gallon which is used in the United Kingdom and semi-officially within Canada, the United States liquid gallon and the lesser used United States dry...

barrels (based on the old English wine measure), the tierce (159 litres) and the 40-US-gallon (151.4-litre) whiskey barrels were used. 45-gallon barrels were also in common use. The 40-gallon whiskey barrel was the most common size used by early oil producers, since they were readily available at the time.

The origins of the 42-gallon oil barrel are obscure, but some historical documents indicate that around 1866, early oil producers in Pennsylvania came to the conclusion that shipping oil in a variety of different containers was causing buyer distrust. They decided they needed a standard unit of measure to convince buyers that they were getting a fair volume for their money. They agreed to base this measure on the more-or-less standard 40-gallon whiskey barrel, but, as an additional way of assuring buyer confidence, they added an additional two gallons to ensure that any measurement errors would always be in the buyer's favor, on the same principle as that underlying the baker's dozen and some other long units of measure. By 1872, the standard oil barrel was firmly established as 42 US gallons.

The abbreviations 1 Mbbl and 1 MMbbl have historically meant one thousand and one million barrels respectively. They are derived from the Latin "mille" meaning "thousand" rather than the Greek "mega". However, this can cause confusion with the SI
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

abbreviation for mega- (and in non-oil industry documentation Mbbl, "megabarrel
SI prefix
The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decadic multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol...

", can sometimes stand for one million barrels).

The "b" may have been doubled originally to indicate the plural (1 bl, 2 bbl), or possibly it was doubled to eliminate any confusion with bl as a symbol for the bale. Some sources assert that "bbl" originated as a symbol for "blue barrels" delivered by Standard Oil
Standard Oil
Standard Oil was a predominant American integrated oil producing, transporting, refining, and marketing company. Established in 1870 as a corporation in Ohio, it was the largest oil refiner in the world and operated as a major company trust and was one of the world's first and largest multinational...

in its early days.

Barrels per day (abbreviated BPD, BOPD, bbl/d, bpd, bd or b/d) is a measurement used to describe the rate of crude-oil production or consumption by an entity. For example, an oil field
Oil field
An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...

might produce 100,000 bpd, and a country might consume 1 million bpd.

Note: BPD is not to be confused with BLPD (barrels of liquids per day), which deals with the total liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

recovered, including water, and not only crude oil. BPD is related to BOE (Barrels of Oil Equivalent)
Barrel of oil equivalent
The barrel of oil equivalent is a unit of energy based on the approximate energy released by burning one barrel of crude oil. The US Internal Revenue Service defines it as equal to 5.8 × 106 BTU...

, a common way of expressing the energy content of hydrocarbon gases in terms of oil, in order to make comparisons.

According to BP
BP
BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...

Statistical Review 2006:
• 1 barrel equals 42 US gallon
Gallon
The gallon is a measure of volume. Historically it has had many different definitions, but there are three definitions in current use: the imperial gallon which is used in the United Kingdom and semi-officially within Canada, the United States liquid gallon and the lesser used United States dry...

s
• 1 BPD = 42/24/60 = .0292 GPM
• 1 GPM = 34.29 BPD
• 1 barrel equals 158.984 Litre
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...

s
• The approximate conversion for BPD to tonnes/year is 49.8, so 100,000 BPD equals around 4,980,000 tonnes per year.

### Conversion to metric units

Care must be taken when converting an oil barrel (bbl) to other units of volume, such as cubic metres (m3). Because oil changes in volume depending upon its pressure and temperature, and the standard temperatures differ slightly between the American conventional and international metric systems, the volume must be corrected to standard conditions for temperature and pressure
Standard conditions for temperature and pressure
Standard condition for temperature and pressure are standard sets of conditions for experimental measurements established to allow comparisons to be made between different sets of data...

if an extremely accurate conversion is required.

Standards bodies such as the American Petroleum Institute
American Petroleum Institute
The American Petroleum Institute, commonly referred to as API, is the largest U.S trade association for the oil and natural gas industry...

(API) have adopted the convention that if oil is measured in oil barrels, it will be at 14.696 psi and 60 °F, whereas if it is measured in cubic metres, it will be at 101.325 kPa and 15 °C (or in some cases 20 °C). The pressures are the same but the temperatures are different — 60 °F is 15.56 °C, 15 °C is 59 °F, and 20 °C is 68 °F. Ignoring the difference between 60 °F and 20 °C may introduce an error of around 0.4%.

The difference in volume depends on the oil's composition, indicated by its density or API gravity
API gravity
The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a petroleum liquid is compared to water. If its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks...

. In warming from 15 °C to 60 °F, a heavy oil with API gravity of 20 (932 kg/m3) will increase in volume by 0.039%. A light oil with API gravity of 35 (848 kg/m3) will increase in volume by 0.047%. Empirically derived lookup tables must be used to do very accurate conversions.

However, if all that is needed is to convert a volume in barrels to a volume in cubic metres without compensating for temperature differences, then this is very straightforward.
• 1 barrel of oil (bbl) is defined as exactly 42 US liquid gallons.
• 1 US liquid gallon is defined as exactly 231 cubic inches.
• 1 inch is defined as exactly 0.0254 metres.

Therefore, 1 bbl = (42 x 231 x 0.02543) m3 = 0.158987294928m3 exactly.

### Barrel per calendar day

Barrel per calendar day (bc/d or bcd) is a standard petroleum downstream industry measurement of actual refinery throughput, as opposed to designed capacity. BPD is computed by dividing the number of refined barrels of oil processed by the number of days in the year. This is contrasted to Barrel per stream day which is computed by dividing the number of refined barrels of oil by the actual number of days the refinery was running.

### Sub units

In terms of production and consumption, it is common to use thousand barrels per day or million barrels per day. These are commonly written as mbd and mmbd respectively taking "m" as the Roman numeral for 1000. It is important not to confuse these with SI
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...

prefixes, where kbd and Mbd would mean a thousand and a million barrels per day respectively.

### Qualifiers

A barrel can technically be used to specify any volume. Since the actual nature of the fluids being measured varies along the stream, sometimes qualifiers are used to clarify what is being specified. In the oil field, it is often important to differentiate between rates of production of fluids, which may be a mix of oil and water, and rates of production of the oil itself. If a well is producing 10mbd of fluids with a 20% water cut, then the well would also be said to be producing 8 thousand barrels of oil a day (mbod).

In other circumstances, it can be important to include gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

in production and consumption figures. Normally, gas is measured in standard cubic feet, but when necessary, this volume is converted to a volume of oil of equivalent enthalpy
Enthalpy
Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.Enthalpy is a...

of combustion. Production and consumption using this analogue is stated in barrels of oil equivalent per day (boed).

In the case of water injection
Water injection (oil production)
Water injection refers to the method in oil industry where water is injected back into the reservoir, usually to increase pressure and thereby stimulate production. Water injection wells can be found both on- and offshore, to increase oil recovery from an existing reservoir...

wells, it is common to refer to the injectivity rate in barrels of water per day (bwd).

• 55 gallon drum
• Barrel
Barrel
A barrel or cask is a hollow cylindrical container, traditionally made of vertical wooden staves and bound by wooden or metal hoops. Traditionally, the barrel was a standard size of measure referring to a set capacity or weight of a given commodity. A small barrel is called a keg.For example, a...

• Barrel of oil equivalent
Barrel of oil equivalent
The barrel of oil equivalent is a unit of energy based on the approximate energy released by burning one barrel of crude oil. The US Internal Revenue Service defines it as equal to 5.8 × 106 BTU...

• English units of wine casks
Below is a list of old English units for wine casks. In addition to the items listed below see separate articles on Gallon, Barrel, Hogshead, Firkin, Puncheon, Butt and Tun.-Rundlet:...

• Imperial units

• Petroleum
• Petroleum pricing around the world
Gasoline and diesel usage and pricing
The usage and pricing of gasoline results from factors such as crude oil prices, processing and distribution costs, local demand, the strength of local currencies, local taxation, and the availability of local sources of gasoline...

• Standard Barrel Act For Fruits, Vegetables, and Dry Commodities
Standard Barrel Act For Fruits, Vegetables, and Dry Commodities
The Standard Barrel Act For Fruits, Vegetables, and Dry Commodities is United States legislation that specified the standard barrel size and measurements for fruits and vegetables, establishing grading standards and inspections for each produce type. It penalized merchants who didn’t use...

• United States customary units
United States customary units
United States customary units are a system of measurements commonly used in the United States. Many U.S. units are virtually identical to their imperial counterparts, but the U.S. customary system developed from English units used in the British Empire before the system of imperial units was...