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API Gravity

Expressing the gravity or density of liquid petroleum products

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API gravity express the gravity or density of liquid petroleum products 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.

  • Oil with the least specific gravity has the highest API gravity
Degree API Specific Gravity Weight 
(lb/US gal) (kg/m3)
8 1.014 8.448 1012
9 1.007 8.388 1005
10 1.000 8.328 998
15 0.966 8.044 964
20 0.934 7.778 932
25 0.904 7.529 902
30 0.876 7.296 874
35 0.850 7.076 848
40 0.825 6.870 823
45 0.802 6.675 800
50 0.780 6.490 778
55 0.759 6.316 757
58 0.747 6.216 745

The formula for API Gravity can be expressed as:

Degrees API Gravity = (141.5 / Specific Gravity at 60oF) - 131.5 (1)

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