API gravity converter
Convert API gravity to specific gravity and density. The scale runs backwards: light oil has the high number.
That's 1.02× as heavy as Brent crude, while medium crude is 1.04× denser. That is light crude: high yields of gasoline and diesel.
What it means
How heavy is that oil?
API gravity is defined at 60 °F. Oil expands with heat, so a field measurement must be corrected to that temperature before the number means anything.
Every unit
Your gravity in every unit
Learn
Three things worth knowing
-
Water is 10 °API
Above 10 floats, below 10 sinks. Brent at 38 °API has a specific gravity of 0.835, so it floats easily.
-
Built from the hydrometer
The scale is a tidied-up version of the older Baumé hydrometer scale, adjusted in 1921 so that the numbers came out round for water and for the crudes of the day.
-
The scale runs backwards
A higher API number means a lighter, less dense oil. Heavy crude at 15 °API is denser than light crude at 45, not the other way round.
Shortcuts
Popular gravity conversions
Background
About API gravity
The American Petroleum Institute scale is built so that water sits at exactly 10: API = 141.5/SG − 131.5. Light crude is above 31, heavy crude below 22, and anything under 10 sinks in water.
Light oil is worth more, because it yields more gasoline and diesel per barrel.