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°API ↔ specific gravity, with crude class.
°API = (141.5 ÷ SG) − 131.5API gravity is measured at 60°F. Water = 10°API. Higher API means lighter, more valuable crude. Edit either field and the other updates.
API gravity is the petroleum industry's measure of how light or heavy a crude oil is compared to water, expressed in degrees (°API). It is calculated from specific gravity with the formula °API = (141.5 ÷ SG) − 131.5, measured at 60°F.
The scale is inverted from density: higher °API means lighter oil. Water sits at exactly 10°API. Crude above 31.1° is light, 22.3–31.1° medium, 10–22.3° heavy, and below 10° extra-heavy (it sinks in water). Light, sweet crude like WTI refines more easily into gasoline and diesel, so it commands a higher price.
Field service & billing software for oilfield service companies — capture tickets at the wellsite, bill in days not weeks.