Oil and gas unit converter

Barrels, Mcf, MMcf and barrels of oil equivalent — with the prefix that means a thousand where SI says a million, and the three different things “a standard cubic foot” turns out to be. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.

Conventions differ, and this page says which it used. Oilfield units carry more than one reading — M is a thousand here and a million in SI, a “standard” cubic foot has at least three pressure bases, and two US agencies publish boe figures 3.45% apart. Check which one the number you are comparing against used.

M means a thousand. Not a million.

This is the single most expensive convention in the industry, and it is a letter. In the oilfield, M is a thousand — from the Latin mille and the Roman numeral M. So Mcf is a thousand cubic feet, and a million is written MMcf: thousand thousand.

In SI, M is mega, and means a million. The same letter, in the same sentence, differing by a factor of a thousand depending on which room you are standing in. It is not a curiosity: reserves, production and sales are all quoted this way, and these are quantities that get sold.

Notice which row is dangerous. MM and B have no SI reading at all, so they are merely unfamiliar — an SI reader stops and asks. M has two readings that are both perfectly sensible, so nobody stops. European companies mostly write kb, mb and gb in lower case for exactly this reason, and it is the better habit.

A barrel is exactly 42 US gallons

Not 55, which is the drum everybody pictures. Forty-two, set by the American Petroleum Institute. And because the US gallon is exactly 231 cubic inches and the inch has been exactly 25.4 mm since 1959, the barrel is exactly 158.987294928 litres. Nothing on this page is measured; it is all arithmetic from definitions.

In cubic feet it is 5.614583… recurring, which has no exact decimal form, so every printed value of it is a rounding.

“Standard cubic foot” is at least three different things

A gas volume means nothing without the temperature and pressure it was measured at, because gas is compressible. Everybody in the US agrees on 60 °F. Nobody agrees on the pressure.

The spread is small and it is not nothing. One standard cubic foot on the 14.73 psi industry base holds 0.231% more gas than one at NIST's 14.696, because the pressure is higher. And the metric standard cubic metre is defined at 15 °C, where 60 °F is 15.56 °C — a colder reference, so a denser one, worth another 0.193%.

Both corrections point the same way. Meeting the two conventions carelessly compounds the error rather than cancelling it — which is the opposite of what most people assume about rounding, and the reason this page makes you choose a basis rather than picking one for you.

A barrel of oil equivalent is a convention, not a conversion

There is no true answer to “how much gas is a barrel of oil”, because it depends on what you are doing with it. So bodies publish conventions, and they publish different ones:

Those are 3.45% apart, on a figure used to report company reserves — so this page gives you both and names which is which, rather than picking one and calling it the answer.

And even agreeing on the energy settles nothing about the money. Oil and gas have never traded at their energy ratio, and the gap between the two has at times been a factor of several. A barrel of oil equivalent is a unit of energy wearing the costume of a unit of oil.

The energy units, and which are exact

Two of those three are exact by construction. The one everybody quotes most is the one that is neither.

Where to go next

API gravity · Unit converter · Hydrostatic pressure