API Gravity Calculator

Petroleum liquids' API gravity is calculated using the API gravity calculator. API gravity is a widely used metric for determining the quality of crude oil. The relative density, or specific gravity, of the crude oil liquid determines the API gravity. This calculator will assist you in determining the API gravity of gasoline or petrol. Continue reading to learn more about the formula for converting specific gravity to API.

What is API Gravity?

When compared to water, the API gravity is a measurement of how heavy a crude oil product is. API gravity refers to the American Petroleum Institute, which created it. Based on the specific gravity of the liquid, the API gravity is computed. The relative density of a liquid is first estimated using a hydrometer or an oscillating U-tube that meets ASTM D1298 or D4052 industrial standards.

API Gravity Formula

After that, the API gravity formula incorporates the specific gravity. The specific gravity of a crude product is calculated using the following formula:

Specific Gravity = 141.5 / (131.5 + API)

When we rearrange the terms, we get: API = (141.5 / Specific Gravity) - 131.5

The formula above can also be referred to as the specific gravity to API conversion formula. According to the equation, the API gravity parameter is dimensionless. It is, however, frequently used in conjunction with a degree symbol, such as the API gravity degree (°API). The following equation can be used to calculate the liquid's specific gravity from its density:

Specific gravity = ρliquid / water, where water has a density of 999 kg/m3. As a result, API gravity can be calculated directly from density.

The API gravity is frequently compared to water, with the relative density of heavy oil at 60 °F being assumed to be 1.0, the same value as pure water. In that situation, the API gravity for pure water will be: API = (141.5 / 1) - 131.5 = 10 °API. This measure is used to assess the behavior of crude goods in water. If a liquid's API gravity is greater than 10° API, it will float on water. If the API gravity value is less than 10, the liquid is heavier than water and will sink.

How do I find out the API Gravity from Specific Gravity?

To find out what a petroleum liquid's API gravity is, do the following:

  • Step 1: Fill in the liquid's density.
  • Step 2: The liquid's relative density will be determined using the calculator.
  • Step 3: The API gravity calculator uses density to calculate the API gravity.

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API Gravity Tables

We can relate API Gravity to its value in a way that the ones having Higher API are lighter crude oil products and are more valuable and can give you high value products. However, crude products having API Values more than 45° are considered less valuable and extra light. Degree of API ranges between 15-45° for majority of the crude products and the most valuable ones being 35-45°.

Degree of API gravity
Crude types
Extra heavy crude
Heavy crude
Medium crude
Light crude
Extra light crude

FAQs on API Gravity Calculator

1. Is API density the same as API Gravity?

The American Petroleum Institute devised a measurement convention for describing the relative density of petroleum liquids to water; the higher the API gravity, the less dense the material.

2. What is API Gravity, exactly?

API gravity is a measurement of a crude oil's or refined product's density. The American Petroleum Institute, or API, is the trade association that developed this metric. The API of crude oil is usually between 15 and 45 degrees. A lighter (lower density) crude has a higher API.

3. Is the API gravity affected by temperature?

The API gravity rises as the temperature rises, whereas the specific gravity falls as the temperature rises. Correlations can be found at Crude oil density as a function of temperature.

4. How is the API gravity used to classify oils?

Oils are classified as light, medium, heavy, or very heavy based on their API gravity. API gravity is extremely essential since an oil's "weight" is the most crucial predictor of its market value. The following are the API values for each "weight": API > 31.1 is considered light.