API Gravity Calculator

- May 10, 2025
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Calculate API gravity, specific gravity, and density conversions for petroleum products. API gravity is a measure used by the petroleum industry to express the relative density of petroleum liquids.

Select Calculation Type

Common Oil Types Reference

Enter Specific Gravity

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About API Gravity

API gravity is a measure of how heavy or light a petroleum liquid is compared to water. If its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks.

Key Formulas
  • API Gravity from Specific Gravity: °API = (141.5 ÷ SG) - 131.5
  • Specific Gravity from API Gravity: SG = 141.5 ÷ (°API + 131.5)
  • Density (kg/m³) from Specific Gravity: ρ = SG × 999
Oil Classifications by API Gravity and Sulfur Content

Crude oils are commonly classified by both their API gravity (density) and sulfur content:

  • Light Sweet Crude: API gravity > 31.1°API with sulfur content < 0.5%. Examples: West Texas Intermediate (WTI) ~ 39-40°API, Brent Crude ~ 38°API, Nigerian Bonny Light ~ 35°API
  • Light Sour Crude: API gravity > 31.1°API with sulfur content > 0.5%. Examples: Russian Urals ~ 31-32°API with ~1.4% sulfur, Mars Blend ~ 28-30°API with ~1.8% sulfur
  • Medium Sweet Crude: API gravity between 22.3-31.1°API with sulfur content < 0.5%. Examples: Louisiana Sweet ~ 30°API
  • Medium Sour Crude: API gravity between 22.3-31.1°API with sulfur content > 0.5%. Examples: Arab Medium ~ 30°API with ~2.5% sulfur, Kuwait Export ~ 30°API with ~2.5% sulfur
  • Heavy Sweet Crude: API gravity < 22.3°API with sulfur content < 0.5%. Examples: Some Indonesian crudes
  • Heavy Sour Crude: API gravity < 22.3°API with sulfur content > 0.5%. Examples: Venezuelan Merey ~ 16°API with ~2.5% sulfur, Mexican Maya ~ 21°API with ~3.5% sulfur, Canadian oil sands ~ 8-12°API with ~4-5% sulfur
  • Extra Heavy Oil: API gravity < 10°API. Examples: Venezuelan Orinoco Belt crudes ~ 8-10°API, Canadian bitumen ~ 8°API
Typical API Gravity Ranges by Petroleum Product
  • Condensate: 50-80°API
  • Petrol: 50-70°API
  • Kerosene/Jet Fuel: 40-50°API
  • Diesel/Heating Oil: 30-37°API
  • Light Lubricating Oils: 28-32°API
  • Heavy Lubricating Oils: 20-28°API
  • Fuel Oil: 12-20°API
  • Bunker Oil: 8-12°API
  • Asphalt: 5-10°API
Economic Importance of API Gravity

API gravity affects the economic value and processability of crude oils:

  • Refining: Light crudes are generally easier to refine and yield more high-value products like petrol and diesel with less processing.
  • Pricing: Light crudes typically command price premiums over heavy crudes due to their superior yield of high-value products.
  • Sweet vs. Sour: Sweet crudes (low sulfur) are more valuable than sour crudes as they require less desulfurisation, which is an expensive process.
  • Transportation: Heavy crudes may require diluents or heating for pipeline transportation, increasing logistics costs.

Understanding API Gravity

API gravity is a way to measure how heavy or light a petroleum liquid is compared to water. If the API gravity is more than 10, it floats on water, while if it's less than 10, it sinks. This measure helps those in the oil industry to classify and compare different types of oils. With our API Gravity Calculator, understanding this concept becomes easy and accessible.

Key Features of the API Gravity Calculator

The API Gravity Calculator offers several features that make it user-friendly and efficient. You can:

  • Calculate API gravity from specific gravity.
  • Determine specific gravity from API gravity.
  • Convert density between different units.

These features cater to various needs in the petroleum sector, from engineers to students studying oil properties.

Selecting Your Calculation Method

When you use this calculator, you start by choosing your calculation method. You can select from three options: calculating API gravity from specific gravity, specific gravity from API gravity, or performing a density conversion. This flexibility allows you to find the information you need quickly and accurately.

Common Oil Types and Their Properties

Another great aspect of the calculator is the reference list of common oil types. Here, you can easily pick from various petroleum types, such as:

  • West Texas Intermediate (WTI) - Light Sweet
  • Brent Crude - Light Sweet
  • Venezuelan Orinoco - Extra Heavy
  • Gasoline
  • Diesel Fuel

This list helps streamline your calculations by providing typical values for specific types of oil.

Inputting Your Data

Once you've selected your calculation type, you can input your data. For API gravity calculations, you’ll need to enter the specific gravity at 60°F. Conversely, if you want to find specific gravity, you’ll input the API gravity value. It's simple and straightforward, ensuring that anyone can use it without hassle.

Understanding the Results

After entering your information, the calculator will provide results for API gravity, specific gravity, and density. Each result is displayed clearly, making it easy to understand. You’ll also find a chart showing oil classifications based on API gravity, which can help you see where your calculations fit within industry standards.

Additional Features for Advanced Users

The calculator isn't just for basic calculations. It also offers advanced options for users who want to consider temperature correction or specify a reference temperature. These features help you gain more accurate results, especially in different conditions, making this tool versatile for professional use.

Learn More About API Gravity

Understanding API gravity is essential in the oil industry. The calculator provides not only the results but also educational resources about the API gravity formula and classifications. This way, you can deepen your knowledge while getting the answers you need, blending functionality and learning seamlessly.