API Gravity Calculator

Category: Physics
- May 22, 2025
| |

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
  • Gasoline: 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 gasoline 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 desulfurization, 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 key measurement in the petroleum industry. It tells you how heavy or light a petroleum liquid is compared to water. If the API gravity is higher than 10, the liquid is lighter and will float on water. If it’s lower than 10, it’s heavier and will sink.

What is the API Gravity Calculator?

The API Gravity Calculator helps you convert between API gravity, specific gravity, and density. Whether you want to find API gravity from specific gravity or the Other way around, this tool makes it simple. It’s designed for anyone working with petroleum, from engineers to students.

How to Use the Calculator

  • Choose the type of calculation you need: API gravity, specific gravity, or density conversion.
  • Select a common petroleum type from the list provided.
  • Enter your values for specific gravity, API gravity, or density as required.
  • Optionally, apply temperature corrections for more accurate results.

Why is API Gravity Important?

API gravity helps determine the quality and value of crude oil. Different grades of oil can be classified based on their API gravity. Lighter oils are usually more valuable because they yield more high-quality products when refined.

Common Oil Types and Their API Gravity

Different types of crude oil are categorized by their API gravity. Some common classifications include:

  • Light Crude Oil: API gravity > 31.1°API
  • Medium Crude Oil: API gravity between 22.3°API and 31.1°API
  • Heavy Crude Oil: API gravity < 22.3°API
  • Extra Heavy Oil: API gravity < 10.0°API

Understanding Density Conversions

Density is another crucial measurement in the oil industry. The calculator can convert between different density units. Whether you need kg/m³, g/cm³, lb/ft³, or lb/gal, this tool has you covered. Understanding density helps in various calculations and ensures accurate results.

API Gravity by Oil Classifications

Producers and buyers often classify oil based on both API gravity and sulfur content. Here’s a brief overview:

  • Light Sweet Crude: API gravity > 31.1°API with low sulfur content
  • Heavy Sour Crude: API gravity < 22.3°API with high sulfur content
  • Medium Sweet Crude: API gravity between 22.3-31.1°API with low sulfur

Final Thoughts on the API Gravity Calculator

The API Gravity Calculator is a valuable tool for anyone involved in the petroleum sector. Its ability to quickly and accurately convert between various measurements makes it essential for decision-making and analysis. Understanding API gravity and related conversions can lead to better resource management and economic benefits.