How to find Barrel : a unit of measurement of oil volume

A barrel is a round container with a convex shape that is wider in the middle than at the top and bottom. They are generally made of wooden slats called staves that are held together with metal hoops.

To find barrel volume, you will need to know its height, radius at the top and bottom, and radius in the middle.

https://www.allmath.com/barrel.php

Barrel Volume Formula

Use the following formula for the total volume of a barrel:

volume = h × π × ((2 × r22) + r12)/3

In the worldwide oil industry, an oil barrel = 42 US gallons, ≈ 159 litres, ≈ 35 imperial gallons.

Thus, the volume of a barrel is equal to the height h times π times two times the middle radius r2 squared, plus the top/bottom radius r1 squared, divided by three.

Oil companies that are listed on American stock exchanges typically report their production in terms of volume and use the units of bbl, Mbbl (1000 barrels), or MMbbl (one million barrels) and occasionally for widest comprehensive statistics the Gbbl (or sometimes Gbl), for giga-barrel (one billion barrels).
There is a conflict concerning the units for oil barrels.
For all other physical quantities, according to the International System of Units, the uppercase letter M means "mega-" (one million), for example, Mm (one million metres, megametres), MHz (one million hertz, or megahertz), MW (one million watts, or megawatt), MeV (one million electronvolts, or megaelectronvolt).
But due to tradition, the Mbbl acronym is used today meaning 1000 bbl, as a heritage of the roman number M meaning 1000.
On the other hand, there are efforts to avoid this ambiguity, and most of the barrel dealers today prefer to use bbl, instead of Mbbl, bbl, MMbbl or mmbbl.


Outside the US, volumes of oil are usually reported in cubic metres (m3) instead of oil barrels.
A cubic metre is the basic volume unit in the International System.
In Canada, oil companies measure oil in m3, but convert to barrels on export, since most of Canada's oil production is exported to the US.
The nominal conversion factor is 1 m3 = 6,2898 oil barrels, but conversion is generally done by custody transfer meters on the border, since the volumes are specified at different temperatures, and the exact conversion factor depends on both density and temperature.
Canadian companies operate internally and report to Canadian governments in cubic metres, but often convert to US barrels for the benefit of American investors and oil marketers.
They generally quote prices in Canadian dollars/m3 to other Canadian companies, but use US dollars/barrel in financial reports and press statements, making it appear to the outside world that they operate in barrels.


Companies on the European stock exchanges report the mass of oil in metric tonnes.
Since different varieties of petroleum have different densities, however, there is not a single conversion between mass and volume.
For example, 1 tonne of heavy distillates might occupy a volume of 6,1 barrels (970 litres; 256 US gallons).
In contrast, 1 tonne of crude oil might occupy 6,5 barrels (1,030 litres; 273 US gallons), and 1 tonne of gasoline will require 7,9 barrels (1,260 litres; 332 US gallons).
Overall, the conversion is usually between 6 and 8 barrels (954 and 1,270 litres; 252 and 336 US gallons)/tonne.