The oilfield runs on a dense shorthand of units that can baffle newcomers. A "barrel" is a precise volume, "Mcf" uses a Roman numeral, and "BOE" lets you add oil and gas together. Here is what the most important units mean.
One barrel (bbl) = exactly 42 US gallons. Gas volumes use M = thousand (Roman numeral), so Mcf = thousand cubic feet. BOE converts gas to oil-equivalent energy at about 6 Mcf ≈ 1 BOE.
Volume and quantity units
The standard unit for crude oil — exactly 42 US gallons (about 158.987 liters). Convert with our bbl to gallons converter.
Gas volume multiples. Natural gas is measured in cubic feet, with the "M" prefix borrowed from the Roman numeral for 1,000:
| Unit | Meaning |
|---|---|
| Mcf | Thousand cubic feet (M = 1,000) |
| MMcf | Million cubic feet |
| Bcf | Billion cubic feet |
| Tcf | Trillion cubic feet |
Barrel of oil equivalent — a way to express gas and oil on one energy basis. By convention, about 6 Mcf of gas ≈ 1 BOE ≈ 5.8 MMBtu of energy. (This is an energy convention, not a price ratio.) Use the BOE calculator.
Energy, gravity and pressure
- BTU — British thermal unit, a measure of energy. Roughly 1 Mcf of gas ≈ 1 MMBtu (about 1.037). Convert with the Mcf to MMBtu converter.
- API gravity — how light or heavy a crude is: API = (141.5 / SG) − 131.5, at 60 °F. Try the API gravity calculator.
- psi — pounds per square inch, the standard unit of pressure in the field.
Drilling and production units
- Mud weight (ppg) — the density of drilling fluid in pounds per gallon. Fresh water is 8.33 ppg; heavier muds hold back higher formation pressures.
- GOR (gas-oil ratio) — the volume of gas produced per barrel of oil, in scf/STB (standard cubic feet per stock-tank barrel).
- Water cut — the percentage of water in the produced liquids. A rising water cut is a common sign of an aging well.
All of our free converters handle these units instantly — barrels to gallons, specific gravity to API, Mcf to MMBtu, and oil-and-gas to BOE.
Built by the team behind OpsFlo — field service & billing software for oilfield service companies. Capture tickets at the wellsite and bill in days, not weeks.
Frequently asked
One barrel (bbl) is exactly 42 US gallons, or about 158.987 liters. You can convert any number of barrels with our bbl to gallons converter.
The M comes from the Roman numeral for 1,000, so Mcf means one thousand cubic feet of gas. MMcf is a million, Bcf a billion, and Tcf a trillion cubic feet.
BOE, or barrel of oil equivalent, converts gas to oil on an energy basis. The standard convention is that about 6 Mcf of gas equals 1 BOE, roughly 5.8 MMBtu of energy. It is an energy measure, not a price ratio.