API Gravity Calculator

Author: Henrick Yau
- 5 August 2026
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Calculators

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

Advanced Options

°C

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 measure that tells us how heavy or light crude oil is compared to water. If the API gravity is higher than 10, the oil is lighter and will float on water. If it's lower than 10, it’s heavier and will sink. This measurement is important in the petroleum industry as it influences how oil is processed and its market value.

Calculating API gravity, specific gravity and density

The API Gravity Calculator helps users calculate API gravity, specific gravity, and density conversions for different petroleum products. With just a few inputs, you can switch between calculating API gravity from specific gravity, specific gravity from API gravity, or performing density conversions. It’s a handy tool for anyone working in oil and gas.

Choosing between API gravity, specific gravity or density conversion

When using the API Gravity Calculator, you can choose from several calculation types. You can calculate:

  • API Gravity from Specific Gravity
  • Specific Gravity from API Gravity
  • Density Conversions

This flexibility allows users to find the information they need quickly and efficiently.

Choosing a Petroleum Type

Another feature of the calculator is the option to select a common petroleum type. You can choose from various options, such as:

  • West Texas Intermediate (WTI)
  • Brent Crude
  • Nigerian Bonny Light
  • Various types of refined products

This selection helps streamline the calculation process, making it easier to get accurate results based on the properties of specific oils.

Entering your specific gravity or API gravity value

To use the calculator, you need to enter specific figures related to your chosen calculation type. For example, if you’re calculating API gravity from specific gravity, you’ll enter the specific gravity value. Likewise, if determining specific gravity, you'll input the API gravity. The calculator is designed to be user-friendly, making it easy to gather the necessary data.

Reading your results and the oil classification chart

Once you enter your data, the calculator provides results in an easy-to-read format. You’ll see values for API gravity, specific gravity, and density. Additionally, you can view an oil classification chart to better understand where your calculated values fit in the spectrum of oil types. This visual aid enhances comprehension of the results.

Setting reference temperature and decimal places

The API Gravity Calculator also offers advanced options to refine your results. You can set a reference temperature and choose how many decimal places you want in your results. This can be particularly useful for more technical applications, ensuring the precision needed in professional environments.

The Importance of Using the API Gravity Calculator

Using the API Gravity Calculator can save time and reduce errors in calculations. This tool is vital for professionals in the petroleum industry, including engineers, analysts, and traders. By simplifying complex calculations, it supports better decision-making regarding oil processing, pricing, and transportation.

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