Petroleum Measurement
API Gravity ↔ Specific Gravity
Convert crude-oil or condensate API gravity and specific gravity using the conventional 60°F/60°F petroleum reference basis.
Defined reference
Temperature basis matters.
API gravity is not a generic operating-density conversion. The standard relationship uses petroleum specific gravity referenced to 60°F relative to water at 60°F.
Calculation basis
°API = (141.5 ÷ SG 60°F/60°F) − 131.5
SG 60°F/60°F = 141.5 ÷ (°API + 131.5)
Higher API gravity corresponds to lower specific gravity on this reference basis.
No observed-density temperature correction is performed here. If the available density/relative-density measurement is at another temperature, use the applicable petroleum measurement procedure before treating it as SG 60°F/60°F.