Physics

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API Gravity Calculator.

Convert liquid specific gravity to API gravity.

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apiGravity: 34.970588

apiGravity

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Use Cases

Classify crude oil

Use API gravity to classify crude oil as light, medium, heavy, or extra heavy. This helps in determining its market value and refining requirements.

Example: If SG = 0.85, API = (141.5/0.85) - 131.5 = 35, indicating light crude.

Check fuel quality

For fuels like gasoline or diesel, API gravity indicates density and quality. Higher API usually means lighter, more valuable fuel.

Example: Gasoline typically has API around 55-60, while diesel is around 30-40.

Frequently Asked Questions

What is API gravity?
API gravity is a measure of how heavy or light a petroleum liquid is compared to water. It is expressed in degrees and is calculated from specific gravity using the formula: API = (141.5 / SG) - 131.5. Higher API means lighter liquid.
How do I use this calculator?
Simply enter the specific gravity of your liquid in the provided field. The calculator will automatically compute the API gravity using the standard formula. No other inputs are needed.
What is the range of API gravity?
API gravity typically ranges from about 10 (heavy) to 70 (light). Liquids with API greater than 10 are lighter than water and will float; those less than 10 are heavier and sink.

Tips & Common Mistakes

Tips

  • Ensure your specific gravity is measured at the standard temperature (usually 60°F) for accurate API gravity.
  • Specific gravity is dimensionless, so no units are needed. Just enter the number.
  • Remember: API gravity is inversely related to specific gravity. Higher SG gives lower API.
  • Use this calculator for quick conversions, but for official reporting, follow industry standards.

Common Mistakes to Avoid

  • Entering specific gravity with units (e.g., kg/m³) instead of a dimensionless number.
  • Confusing API gravity with Baume gravity; they are different scales.
  • Assuming API gravity is linear with density; it is not, it's an inverse function.

Last updated: August 13, 2026