API gravity express the gravity or density of liquid petroleum products
API gravity express the gravity or density of liquid petroleum products. API is devised jointly by the American Petroleum Institute and the NIST - National Institute of Standards and Technology. The measuring scale is calibrated in terms of degrees API.
API Gravity can be calculated as:
API = (141.5 / SG) - 131.5 (1)
API = Degrees API Gravity
SG = Specific Gravity (at 60oF)
- Oil with the least specific gravity has the highest API gravity
SG - API Converter
SG - Specific Gravity
|Degree API||Specific Gravity||Weight|
- There area no clear definition of the different classes of crude; heavy, middle, light etc. Different sources and different countries uses their own limits. The boxes in the figure indicate the most common ranges used.