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How Much Does a Gallon of Gas Weigh (and Why Is It Important)?

Knowing how much a gallon of gas weighs is an important safety factor for RVers (or any vehicle that carries a heavy load). And from diesel to octane to propane, the weights of each are slightly different. 

Whether you’re new to RVing and towing, or have been doing it for years, there are few things more valuable than knowing the weight of your rig. And the weight of gasoline plays a role in that. 

Today, we’ll share fuel weights and walk you through why it’s significant to know.

Let’s go! 

Why Is It Important To Know How Much a Gallon of Gas Weighs?

Rather than just knowing how much a gallon of gas weighs, consider how much your RV weighs. There’s the weight as specified by the manufacturer. Then there’s the weight once you equip it with all your stuff. 

There are several things to consider. Are you driving a motorhome or pulling a towable? Maybe you’re driving a motorhome and pulling a towable. Perhaps you upgraded to a larger freshwater tank and added a hitch carrier with all the family bicycles. 

Each recreational vehicle has a rate for a certain amount of weight. Likewise, each tow vehicle has a maximum towing capacity. This is for optimum performance, but more importantly, safety. 

How much your setup weighs can help you avoid hazardous situations like tire failure. You may need to cross a bridge and want to know if you’re within the structure’s load limits. 

If axles are overloaded, it can strain the suspension components. These parts could fail. This could lead to losing control of your vehicle and potentially causing an accident. 

If you’re pulling over the capacity of your truck, you can do a lot of damage there, too (think engine and transmission, shudder). No one wants to be “that guy” on the side of the road, hood up because the engine overheated. 

Okay, how much does that gallon of gas weigh? 

Close up of red gasoline canister
A standard gallon of gas will weigh about six pounds, but it will vary depending on the type of gas used.

So, How Much Does a Gallon of Gas Weigh?

The weight of gas can be a tad complicated because it depends on the grade, plus temperature and quality. A basic gallon of standard gasoline is 6.0 pounds. Higher grades, 91 or 93 octanes, are 6.1 pounds.

But wait. Are you using diesel fuel? The average weight of diesel is about 7.0 pounds per gallon.

Consider propane. At room temperature, one gallon of propane weighs 4.11 pounds. And don’t forget the weight of the tank too. 

These may seem inconsequential. But every pound counts when you’re long-hauling it through the desert or steep climbing up mountain roads.

Why Does a Gallon of Gas Weigh Less Than a Gallon Of Water?

Why is gasoline lighter than water? The answer lies in science, of course. 

Water is composed of hydrogen and oxygen. The small oxygen molecules are tightly packed together, which gives water a greater density. 

Gases, or hydrocarbons, are typically composed of hydrogen and carbon. The carbon atom is lighter than oxygen. Hence, gas is less dense. 

The hydrocarbon molecule is bigger and not as tightly packed as water. It takes less gas to fill up the same space. This is also why gas floats on water. 

Thanks for letting us geek out there for a moment. 

Does the Weight of Gas Change With the Weather?

Regardless of your gas type, the weight increases as the temperature decreases. It fluctuates with humidity, temperature, and weather changes (think barometric pressure.) Hot weather causes gas molecules to expand, and cold weather causes the molecules to contract. 

If you’re traveling between climate extremes, you can find weight converters online that include temperature. For example, climbing that mountain in freezing temperatures of 30 degrees Fahrenheit can take your diesel fuel weight to 7.1 pounds per gallon. 

Pro Tip: Check out these 14 examples of different RVs to uncover How Much Do RVs Weigh?

Truck weigh station sign
Knowing how much your RV weighs is important while on the road.

Where Can I Weigh My RV?

Wake up! Science class aside, let’s get that RV weight figured out. Load up as if you were headed out for a trip – gas, water, accessories, and the family. You want as realistic a weight as possible.


Certified CAT scales, or truck scales, are at most truck stops. You don’t need to make an appointment. Just show up with your rig and drive onto the platform scales. 

Have a friend or family member help ensure each axle is on a different scale. If you’re pulling a towable, you want to get the truck on a separate scale. Both pieces of your rig need weighing for accuracy on your complete setup. 

Talk to the clerk inside if you’re not sure you have it right or have a more extensive motorhome setup. The process takes just minutes, and you’ll get a report at the register. You get peace of mind for the nominal price of between $10 and $25. 

Escapees Smart Weigh

The four-corner Smart Weigh gives you more specific information. It’ll not only give you the total weight of your RV but also provide the weight riding on each wheel position. This helps when you’re trying to balance your load and distribute weight evenly.

Finding this type of scale is tougher. Start by checking your RV club. They may know where to find specific weigh stations. 

The Escapees RV Club is a 40-year-old support network for RVers. They provide a host of services beyond Smart Weigh. In addition to the weight distribution, you get the height of your rig too. We think this method provides valuable information for an estimated cost of $60 to $100. 

RV Shows and Rallies

There are other locations to get basic weight for your RV. In addition to CAT scales and Smart Weigh, farm co-ops and sand and gravel yards have scales. Some moving and storage companies may also provide the service. 

RV shows and rallies are other good options. The experts there know what to look for and how to help you get the correct information.

Pro Tip: Head to one of these 7 Best RV Shows in 2022 to get your RV weighed.

Be Smart, Know Your RV’s Weight

Savvy RVers know that safety and performance are a must. The amount of gas you have in your RV and stored for other uses may not seem a big deal. In reality, everything in your recreational setup is critical. And knowing how much a gallon of gas weighs can help you manage your RV’s load balance.

As the old saying goes, “A pound of prevention is worth a pound of cure,” or the weight of a gallon of gas.

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