Semi-trucks are impressive vehicles. They can travel long distances and haul immense loads. But just how many gallons of fuel does a semi-truck hold and what does that translate to for distance? Furthermore, how much does this weigh?

How many gallons of fuel does a semi-truck hold: A semi-truck has a fuel tank with a capacity of 120 to 150 gallons. Some semi-trucks have only one fuel tank while others have two tanks, both with the same capacity. Trucks that drive through remote areas will need a double tank. Generally, most drivers will only fill their fuel tanks up to 95% capacity. This is to decrease the risk of spills and to allow the fuel to expand in hot temperatures.

How much does the fuel in a semi-truck gallon weigh?

On average, one gallon of diesel fuel will weigh about 7 pounds. Factors such as fuel grade and temperature can slightly alter this weight.

That means that the fuel in a semi truck can weigh around 840 – 1050 lbs for a single tank, or 1640-2100 lbs if the semi truck has a double fuel tank.

Diesel fuel is now a lot cleaner than it used to be, which means the fuel is purer. Even if diesel hasn’t decreased in weight, it is more efficient.

How many miles does a semi-truck go from a gallon?

The size of a semi-truck is massive and with extra weight comes a larger fuel consumption. The more a semi-truck is carrying, the harder the engine needs to work.

On average, a semi-truck can expect to get between 7 and 8 miles per gallon. This is not a lot.

In contrast, the average car can expect to get 25.7 miles per gallon; our company has a GMC Sierra pickup truck, and it averages 15.4 miles per gallon for example.

If a semi-truck is driving along a flat route, it can expect to get better gas mileage while this number can be cut almost in half if there are steep hills the semi-truck needs to drive up.

How much fuel do you need to put in a semi-truck?

How much fuel do you need to put in a semi-truck

The actual size of a fuel tank in a semi-truck will vary according to manufacture. Newer semi-trucks usually have larger tanks, whereas older ones will have smaller ones.

Larger tanks mean less stopping for truck drivers, which increases the profit margins as goods are delivered quicker.

A fuel tank in a semi-truck can have a capacity of between 120 and 150 gallons. In other terms, this is between 450 and 560 liters.

There are now some semi-trucks that will have two fuel tanks onboard. Each tank will still be between 120 and 150 gallons.

This will increase the overall weight of the truck but will also allow them to drive for longer distances.

Having a second fuel tank is essential if a driver is out in remote parts of the world where they aren’t sure about having regular access to a fuel station.

How much does a full tank of diesel fuel weigh?

A bit of math is needed to figure out the total weight of a semi-truck’s fuel tank. Start with the math where one gallon of fuel weighs 7 pounds.

Then, look at what 95% of the total tank allotment is. Finally, you can multiply the two numbers.

120 gallons: 120 x .95 x 7 = 798

150 gallons: 150 x .95 x 7 = 998

So, if you have a 120-gallon tank that is filled to 95% capacity, it will weigh 798 pounds and for a 150-gallon tank, it will weigh 998 pounds.

Keep in mind that a truck driver’s maximum load capacity includes the cargo, the weight of the truck, and the fuel. This is why knowing the equation is so beneficial. It allows you to better plan your trip and shipping abilities.

Things to consider when filling up your semi-truck fuel tank

Even though you want as much fuel in your tank as possible when you start out on a journey, most truck drivers will stick to the 95% rule. This is where you only fill your fuel tank up to 95% of the way. There are many reasons for this, which we’ll expand on below.

Risk of Spilling

There is always a risk of spilling when filling up, and more so with a semi-truck. There is both a main tank and an overfill tank in a semi-truck but if too much fuel is in the main tank, too much can enter the overfill area.

As a result, you can end up wasting fuel, which costs money, especially as gas prices continue to rise.

Furthermore, even if only a small amount of fuel falls to the ground, this is still an environmental hazard. Any amount of fuel on the ground can lead to issues for other drivers.

Fuel Expansion

Anytime fuel is warmed up, it will expand. If you are a truck driver who is driving in the middle of summer, the fuel in your tank can easily exceed its limitations.

Even a small increase in the temperature around your fuel can lead to an increase in volume. This is why it is important to leave room for expansion.

Fuel Weight

Yes, a semi-truck wants to start out on any journey with a full tank of fuel but this weight affects the maximum load allowance of a truck.

Semi-trucks have a weight capacity of between 70,000 and 80,000 pounds. Companies that employ semi-truck drivers will want to go as close to this maximum as possible to offset the high costs of paying drivers.

However, if a semi-truck weighs more than the maximum, it can have terrible consequences.

Not only can it cause damage to the truck and its engine, but it can tear holes in the pavement and create deep grooves that need to be fixed, or result in fines for the operator or trucking company.

Weight Changes – Temperature

In cold weather, diesel fuel can contract, and if it get cold enough, the fuel will gel.

Or, if there is an increase in temperature, it can actually make the fuel take up more space as it expands.


A semi-truck will have a fuel tank with a capacity of between 120 and 150 gallons but most drivers only fill this to 95%. This is in order to compensate for such issues as fuel expansion and a risk of spilling.