API gravity is the petroleum industry’s inverse-SG scale. API = 141.5/SG − 131.5 (both at 60 °F).
Formula
$$ \text{API} = \frac{141.5}{SG_{60}} - 131.5 $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $SG_{60}$ | Specific gravity at 60 °F | - | densitometer / hydrometer |
| $API$ | API gravity | °API | result |
Sources
- API MPMS Chapter 11.1.