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- Definition: API Gravity is a measure of the density or weight per unit volume of petroleum liquids relative to water. It is calculated using the following formula:
\[
\text{API Gravity} = \left( \frac{141.5}{\text{Specific Gravity at } 60^\circ \text{F}} \right) – 131.5
\]
where Specific Gravity is the density of the petroleum liquid compared to water at the same temperature. - Usage: The API Gravity scale is widely used in the petroleum industry to classify crude oil and other liquid hydrocarbons. Higher API Gravity values indicate lighter oils, while lower values indicate heavier oils. For instance, a higher API Gravity (above 10) indicates a lighter crude oil that typically yields higher proportions of gasoline and diesel when refined.