What Is Barrel (Oil)?
A barrel of oil is a unit used to measure how much crude oil or petroleum product there is. It tells us the volume, which means the space the liquid oil fills.
Oil companies, governments and traders use barrels to talk about how much oil they produce, move, store, buy and sell.
Definition
In the modern oil industry, one standard barrel of oil is defined as:
- 42 US liquid gallons of oil
- About 159 liters of oil
- About 0.159 cubic meters of oil
A barrel of oil is a unit of volume, not weight. This means it measures how much space the oil takes up, not how heavy it is. The weight of a barrel of oil changes with the type of oil because some oils are thicker or lighter than others.
History / Origin
The barrel of oil unit began in the early days of the modern oil industry in the 1800s in the United States, especially in Pennsylvania.
At that time, people did not have special metal tanks for oil. Instead, they reused wooden barrels that were first made to hold things like fish, food and other goods. These wooden barrels were common, strong and easy to move.
Different sizes of barrels were used at the start, which caused confusion. To make trade easier and more fair, oil producers agreed to use one standard size. They chose a 42 gallon barrel as the official measure. Over time this 42 gallon size became the world standard for a barrel of crude oil.
Today most oil is not physically moved in wooden barrels. It travels in pipelines, ships, rail cars and trucks. The word barrel now mostly means the unit of measurement, not the actual container.
Symbol & Abbreviation
The common symbol and short forms for the barrel of oil are:
- bbl meaning one barrel of oil
- bbls meaning more than one barrel of oil
In reports and on trading screens you may also see:
- Mbbl for a thousand barrels of oil
- MMbbl for a million barrels of oil
- bbl d or bpd for barrels per day, a rate of production or use
These short forms make it easy to write large numbers and to compare output and demand between countries or companies.
Current Use Around the World
The barrel is still the main unit used in the global oil and gas industry, even in countries that use the metric system.
Typical uses include:
- Production Oil fields and countries report how many barrels of oil they produce per day.
- Consumption Energy reports show how many barrels of oil people and industries use in a day or a year.
- Reserves Oil reserves are given in millions or billions of barrels to show how much oil may be recovered in the future.
- Trading Oil prices on markets like Brent and WTI are quoted in dollars per barrel.
- Transport and storage Tank sizes, ship cargo and storage capacity are often expressed in barrels.
In technical work and science, people also use metric units like cubic meters and liters. Many countries use both units together, for example barrels for news and reports, and cubic meters for engineering work, taxes and rules.
Example Conversions
Here are some simple conversions for one standard barrel of oil using rounded values that are good for everyday use:
- 1 barrel of oil = 42 US gallons
- 1 barrel of oil ≈ 159 liters
- 1 barrel of oil ≈ 0.159 cubic meters
- 10 barrels of oil ≈ 1.59 cubic meters
- 100 barrels of oil ≈ 15.9 cubic meters
Some useful back conversions:
- 1 US gallon of oil ≈ 0.0238 barrels
- 1 liter of oil ≈ 0.00629 barrels
- 1 cubic meter of oil ≈ 6.29 barrels
Approximate weight examples for medium crude oil this changes with oil type:
- 1 barrel of medium crude oil ≈ 135 to 160 kilograms
- About 6 to 7 barrels of such crude ≈ 1 metric ton
Small comparison table using rounded figures:
| Barrels of oil | US gallons | Liters | Cubic meters |
|---|---|---|---|
| 1 bbl | 42 | 159 | 0.159 |
| 10 bbl | 420 | 1 590 | 1.59 |
| 100 bbl | 4 200 | 15 900 | 15.9 |
Related Units
The barrel of oil is often used together with these related units:
- Liter (L) A metric unit of volume. 1 barrel is about 159 liters.
- US liquid gallon A volume unit used in the United States. 1 barrel is 42 US gallons.
- Cubic meter (m³) A common metric unit for large liquid volumes. 1 cubic meter is about 6.29 barrels.
- Metric ton of crude oil A unit of mass. The number of barrels in a ton changes with oil density, but it is often around 6 to 8 barrels per metric ton.
- Barrels of oil equivalent (boe) A unit used to compare the energy in oil, gas and other fuels by saying how many barrels of oil would have the same energy.
- Barrels per day (bpd or bbl d) A flow rate that shows how many barrels are produced, used or moved each day.
FAQs
Is a barrel of oil a real barrel?
Not usually. In the early days, oil was stored in wooden barrels. Today oil mostly moves through pipelines and large metal tanks. The word barrel is now mainly a measuring unit, not a container.
Why is one barrel of oil 42 gallons?
In the 1800s, oil producers in the United States agreed to use a 42 gallon wooden barrel as the standard size. It was a common, practical container. This standard stayed and is still used worldwide.
Is a barrel of oil a measure of volume or weight?
A barrel of oil measures volume, the space the liquid takes up. It does not directly tell you the weight. The weight depends on how dense or thick the oil is.
Are all barrels the same size?
No. There are other kinds of barrels used for beer, wine or chemicals, and they can have different volumes. When people say barrel in the oil industry, they almost always mean the 42 gallon oil barrel.
How many liters are in one barrel of oil?
One standard barrel of oil is about 159 liters. The exact value often used is 158.987 liters, but 159 is close enough for most everyday uses.
Why do some reports use barrels and others use cubic meters?
Barrels are traditional in the oil business and are common in news and trading. Many countries and engineers prefer cubic meters because it is a metric unit that fits better with other scientific and technical measures. Both units describe the same volume, just in different systems.