User:Milton Beychok/Sandbox

The API gravity is an arbitrary scale developed by the American Petroleum Institute (API) as a measure of the density of petroleum liquids relative to the density of water. The values of API gravity are expressed as degrees API denoted as °API.

Relationship between API gravity and specific gravity

The relationship between API gravity and specific gravity (SG) of a petroleum liquid is mathematically expressed as:

$^{\circ }\mathrm {API} ={\frac {141.5}{\mathrm {SG} _{60\,^{\circ }\mathrm {F} }^{60\,^{\circ }\mathrm {F} }}}-\mathrm {131.5}$

and where:

$\mathrm {SG} _{60\,^{\circ }\mathrm {F} }^{60\,^{\circ }\mathrm {F} }={\frac {\mathrm {density\;of\;water\;at\;60\,^{\circ }\mathrm {F} } }{\mathrm {density\;of\;petroleum\;liquid\;at\;60\,^{\circ }\mathrm {F} } }}$

Conversely, the specific gravity may be obtained from the API gravity by this expression:

$\mathrm {SG} _{60\,^{\circ }\mathrm {F} }^{60\,^{\circ }\mathrm {F} }={\frac {141.5}{^{\circ }\mathrm {API} +131.5}}$