API Degree To Specific Gravity Calculation

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API gravity is a measure comes from American Petroleum Institute of how heavy or light a petroleum liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks.

This is not a brand new formula but very handy calculation to have. The important calculation for Petroleum Engineer.

API Gravity = ( 141.5 / Specific Gravity ) – 131.5

Specific Gravity = 141.5 / ( 131.5 + API )

Example: pure water at 60 deg F with  a specific gravity of 1.0 would have an API gravity:

API Gravity = ( 141.5 / 1.0 ) – 131.5 = 10 deg API

The principle is low API Gravity is mean height density  petroleum

10 1.000
15 0.966
20 0.934
25 0.904
30 0.876
35 0.850
40 0.825
45 0.802
50 0.780
55 0.759
60 0.739


API Gravity Chart

API Gravity Chart

Classification crude oil based on API degree

  • Light Oil

Light oil is conventional oil with API gravity minimum 22° and viscosity less than 100 centipoise (cp), this type crude oil is can flow naturally no need to steam.

  • Heavy Oil

Low density crude oil and viscous is normally have API gravity less than 22°

  • Extra Heavy Oil

Extra Heavy oil normally heavier than heavy oil and also have API gravity less than 10°

  • Oil Natural Bitumen ( Extra-Heavy Crude Oil )

Also called oil sands, oil bitumen shares the attributes of heavy oil but have more viscosity and also the viscosity is greater than 10.000 cp

See table bellow to crude oil classification based on API Degree

Classification Crude Oil Based On API Gravity

Classification Crude Oil Based On API Gravity

Find the link for API calculator spreadsheet bellow and also looks table bellow for API Chart

Thanks For reading API Degree To Specific Gravity Calculation

API Gravity Calculator and Conversion

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    Hero Santoso Effendi Petroleum Engineer From Indonesia, working on oil and gas industry. Bachelor Degree on Petroleum Engineer UPN Veteran Yogyakarta University. Working and learning hard sharing for complete my life. Programmer is my other skill. Find Me on Link below :

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