API Gravity: Definition, Calculation, and Converter

API expresses the gravity or density of liquid petroleum products. It is devised jointly by the American Petroleum Institute and NIST.

Formulas

API Gravity from Specific Gravity:

°API = (141.5 / SG) - 131.5

Specific Gravity from API Gravity:

SG = 141.5 / (°API + 131.5)

Where:

°API = Degrees API Gravity
SG = Specific Gravity (at 60°F)

Note: Oil with the least specific gravity has the highest API gravity. Density is temperature-dependent; the standard measuring temperature is 15°C or 60°F.

Degree API	Specific Gravity	Weight (lb/US gal)	Weight (kg/m³)
1	1.068	8.894	1067
5	1.037	8.633	1035
8	1.014	8.447	1013
10	1	8.328	998.9
15	0.9659	8.044	964.8
20	0.934	7.778	933.1
25	0.9042	7.53	903.2
30	0.8762	7.297	875.3
35	0.8498	7.078	848.9
40	0.8251	6.871	824.3
45	0.8017	6.677	800.8
50	0.7796	6.493	778.8
55	0.7587	6.319	757.9
60	0.7389	6.154	738.1
70	0.7022	5.848	701.5
80	0.669	5.572	668.3
90	0.6388	5.32	638.1

Degree API

Specific Gravity

Weight (lb/US gal)

Weight (kg/m³)

1.068

8.894

1067

1.037

8.633

1035

1.014

8.447

1013

8.328

998.9

0.9659

8.044

964.8

0.934

7.778

933.1

0.9042

7.53

903.2

0.8762

7.297

875.3

0.8498

7.078

848.9

0.8251

6.871

824.3

0.8017

6.677

800.8

0.7796

6.493

778.8

0.7587

6.319

757.9

0.7389

6.154

738.1

0.7022

5.848

701.5

0.669

5.572

668.3

0.6388

5.32

638.1

API Gravity: Definition, Calculation, and Converter

API Gravity: Definition, Calculation, and Converter

Formulas

Inputs

Results