API ↔ SG Converter
API gravity is the petroleum industry's inverse-SG scale. API = 141.5/SG − 131.5 (both at 60 °F).
API gravity
27.49°API
Specific gravity (60 °F)
0.8900 -
Formula, assumptions, and limits
$$\text{API} = \frac{141.5}{SG_{60}} - 131.5$$
API = 10 → water density. Light crude 35–45; medium 25–35; heavy 15–25; VLSFO/HFO 10–20. Conversion defined at 60 °F (15.56 °C); density must be temperature-corrected before using.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $SG_{60}$ | Specific gravity at 60 °F | - | densitometer / hydrometer |
| $API$ | API gravity | °API | result |
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