A gallon of gasoline weighs around 2,819 grams or 6.2 pounds. This is the approximate weight of one U.S. liquid gallon of gasoline at 15.5°C (60°F). However, the exact weight can vary slightly depending on the gasoline’s density and composition.
What is the density of gasoline?
Gasoline is a liquid fuel made from petroleum. Its density, or mass per unit volume, can range from 0.71 to 0.77 grams per cubic centimeter (g/cm3) in the U.S. This depends on factors like the crude oil source, refining process, and additives used. The density equates to around 6.0 to 6.4 pounds per U.S. gallon.
Typical density range
Most gasoline blends sold in the U.S. fall between 0.72 to 0.78 g/cm3 density. This includes common fuel grades like regular (87), midgrade (89), and premium (93). Heavier fuels like diesel and kerosene tend to have higher densities.
Lighter blends
Some specialized blends using more light hydrocarbons can be less dense. For example, a high-octane racing fuel may have a density around 0.71 g/cm3. This lower density equates to about 5.9 lbs/gal. The fuel weighs less but also contains less energy per gallon.
Ethanol blends
Adding ethanol can decrease gasoline’s density slightly. E10 fuel with 10% ethanol may have 0.75 g/cm3 density versus 0.76 g/cm3 for non-ethanol gasoline. This small change in density equals around 6.1 lbs/gal for E10 instead of 6.4 lbs/gal.
Calculating weight from density
We can calculate the weight in grams of 1 gallon of gasoline from the density in g/cm3 using the following equation:
| Weight (g) | = | Density (g/cm3) | x Volume (cm3) |
Since 1 U.S. liquid gallon equals 3,785 cm3, we can plug this into the equation to get:
| Weight (g) | = | Density (g/cm3) | x 3,785 cm3 |
As an example, if the gasoline density is 0.75 g/cm3, the calculation would be:
| Weight | = | 0.75 g/cm3 | x 3,785 cm3 |
| 2,839 grams |
This shows that 1 gallon of 0.75 g/cm3 gasoline weighs around 2,839 grams or 6.1 pounds. We can calculate the weight for any given density using this method.
Typical gasoline weight
Based on typical gasoline densities, 1 U.S. gallon of gasoline usually weighs between:
- 2,690 g (5.9 lbs) for very light blends
- 2,839 g (6.1 lbs) for regular grades with ethanol
- 2,868 g (6.2 lbs) for standard grades
- 3,004 g (6.4 lbs) for very dense grades
So the average density of 0.75 g/cm3 corresponds to about 2,819 grams or 6.2 pounds per gallon. This approximate weight at standard conditions (15.5°C/60°F) is often used for calculation purposes involving gasoline amounts and fuel economy.
What affects density?
Several factors can influence the density of gasoline:
Chemical composition
Gasoline contains a mixture of hydrocarbons including paraffins, naphthenes, olefins, and aromatics. The chemical structure and molecular weight of these compounds affects overall density. Lighter hydrocarbons result in lower density.
Additives
Additives like ethanol and fuel system cleaners change the density slightly. Oxygenates like ethanol decrease density while detergent additives increase it marginally.
Temperature
Gasoline density decreases as temperature increases. This is why the standard reference condition for density is 15.5°C (60°F). Colder fuel is slightly denser.
Quality control
Variability in crude oil feedstocks and refining processes can cause small density differences. Fuel standards regulate key specifications to minimize variations among brands and grades.
Does density affect performance?
Density correlates with a gasoline’s energy content. Lower density means less mass and energy per gallon. Under U.S. fuel economy testing standards, the EPA assumes an average gasoline density of 0.745 g/cm3. Vehicles do get slightly worse fuel economy from lower density blends in real-world driving.
How is gasoline density measured?
Gasoline density is precisely measured using a hydrometer, pycnometer, or digital density meter. ASTM D4052 and D1298 cover standard test methods for determining density and specific gravity. Refineries, third-party labs, and regulatory agencies analyze gasoline samples to ensure specifications are met.
Converting between density, specific gravity, and API gravity
Gasoline density can also be expressed using:
- Specific gravity (SG) – The ratio of gasoline density to water (SG = 1)
- API gravity – An inverse measure of density developed by API (higher value = lower density)
The following equations show how to convert between these terms:
| SG | = Density of gasoline / Density of water |
| API Gravity | = (141.5 / SG) – 131.5 |
| Density | = SG x Density of water |
So a gasoline with 0.75 g/cm3 density would have:
- Specific gravity (SG) = 0.75 g/cm3 / 1 g/cm3 = 0.75
- API gravity = (141.5 / 0.75) – 131.5 = 60
Typical API gravity of gasoline
Most gasoline sold in the U.S. has an API gravity between:
- 50-60 API: Midgrade and premium grades
- 60-70 API: Regular grade gasoline
- 70+ API: Light racing fuels
An average API gravity of around 62 corresponds to 0.75 specific gravity and 0.745 g/cm3 density under standard conditions.
Does gasoline weight matter?
Knowing the weight of gasoline is useful for transportation, regulation, and engineering purposes. Some examples include:
- Calculating fuel economy in miles per gallon
- Sizing storage tanks and pipelines
- Measuring compliance with environmental rules
- Estimating shipping weights and costs
- Balancing refinery inputs and outputs
- Understanding differences between gasoline blends
So while a few grams difference in gasoline weight per gallon may not matter to individual consumers filling their gas tank, it has important implications at larger commercial scales.
Weight vs. volume as a measurement
Gasoline is bought and sold by volume in gallons, but weighed in bulk quantities like tanker trucks or rail cars. At cold temperatures, the same volume of dense gasoline weighs more. Some key considerations include:
- Volume is easier to measure accurately for retail transactions
- Weight changes with temperature, while volume stays fixed
- Heavier blends contain more energy per gallon
- Lighter blends can improve vehicle fuel economy
So gasoline weight affects transportation logistics and fuel efficiency, while volume determines how much fits in a gas tank. Understanding the connections between density, weight, and volume is important for managing gasoline supplies.
Conclusion
In summary, gasoline typically weighs between 2,690-3,004 grams per U.S. gallon depending on density, with 2,819 g/gal being a reasonable average. This equates to around 6 pounds per gallon under standard conditions. Factors like chemical composition, additives, temperature, and quality control lead to small density variations among different types of gasoline. Converting between density, specific gravity, and API gravity provides alternate ways to represent gasoline weight. While gasoline is sold by volume, its weight matters for calculating fuel economy, sizing storage and pipelines, and other commercial applications.
