API gravity is measure of the density of liquid hydrocarbons relative to water. This article provides a reference to the API gravity calculation formula and some typical values of API gravity for common hydrocarbons.


SG:Specific gravity

Calculation of API Gravity

API gravity is a standard scale by which the density of hydrocarbons can be characterised relative to water. It is useful as many correlations have been developed over the years to estimate the properties of hydrocarbons as a function of API gravity.

The only information required to calculate the API gravity is the specific gravity or density of the hydrocarbon. The API gravity may be calculated using the following formula:

The API gravity is usually reported using the degree symbol, for example an diesel fuel may be said to be 42° API.

Reference Values for API Gravity

The table below contains the API gravities of some commonly report hydrocarbons.

° API Name
4-10Extra Heavy Crude
38Brent Crude
39.6West Texas Intermediate
27-42Light Crude Oil
42Diesel Fuel