How Many Gallons In a 40 lb Propane Tank? (Propane Tank Sizes)

How Many Gallons In a 40 lb Propane Tank

Do you know how many gallons are in a 40 lb propane tank? Well, you are at the perfect place to find the answer to such a question.

There are many different sizes of propane tanks out there and for some uses, you’re going to need something a bit larger.

A 40 lb propane tank holds 40 lb of propane, right? Well, not exactly.

To put it simply, on average you have 0.236 gallons = 1 pound of propane.

If you’re looking to fuel a large commercial grill or get a bit of extra heating onto your patio then you might be wondering, how many gallons are there in a 40 lb propane tank?

On average a 40 lb propane tank can hold around 9-10 gallons of propane, or between 40 and 45 liters. This size of tank is reasonably large and usually requires a trolley for easy transportation, but it has a good capacity that is well suited to larger appliances. In reality, a 40 lb propane tank is about 80% full, so the most you can put in is 8 gallons.

This article will go into detail about these particular propane tanks, including exactly how much fuel a 40 lb tank can contain, how long it is likely to last, and options you have when your tank starts to run low.

Exactly How Much Fuel Does a 40 lb Propane Tank Hold?

The exact quantity of propane contained within a tank of this size can vary slightly. 40 lb propane tanks hold between 9 and 10 gallons of propane, but the average is between 9.2 – 9.4 gallons. This equates to around 41 – 43 liters of propane fuel inside the tank when it is full.

9 – 10 gallons is a pretty reasonable quantity of fuel. In fact, it is double that of the average tank, which is the 20 lb size. 40 lb propane tanks are usually best suited for bigger appliances, commercial uses, space heaters, and other medium-to-high BTU equipment.

Read also: Cheapest Propane Refill Near Me (Tanks Exchange Locations)

How Large is a 40 lb Propane Tank?

These tanks are not completely unwieldy, but they are certainly less portable than a 5 of 10 lb tank. Usually, a tank of this size is quite tall, and they are heavy enough that you would find it uncomfortable to carry them over any significant difference.

To move these tanks around, it is best to use a trolley with wheels.

The exact dimensions of a 40 lb tank of propane will depend on the shape of the tank that you use, but the most common measurements are:

  • Width: Approximately 12 inches
  • Depth: Approximately 12 inches
  • Height: Approximately 30 inches

Read also: How Many Gallons In a 10 lb Propane Tank? (Propane Tank Sizes)

How Much Does a 40 lb Propane Tank Weigh?

The weight of any propane tank depends very much on how much fuel it still has inside. The 40 lb descriptor refers to the approximate weight of a full tank of fuel, but the tank itself will have an empty weight as well.

The empty tank weight is usually referred to as the “tare weight” (or TW) which should be engraved somewhere on the exterior.

Most 40 lb propane tanks have a TW of around 32 lbs. If you combine this with the 40 lbs that the tank can hold in fuel, then it will weigh a total of about 72 lbs when it is filled with propane. This is quite a significant weight which many people find challenging to lift without assistance.

Despite the fact that they are so difficult to lift when they are full, 40 lb tanks are still popular among some RV and camping enthusiasts because they don’t need to be refilled as often as smaller tank options.

Read also: How Many Gallons In a 50 lb Propane Tank? (Propane Tank Sizes)

How Long Will a 40 lb Propane Tank Last?

One of the most important things about buying a propane tank is how many hours of use you will get out of it. At the end of the day, it all depends on the appliances that you are going to use your tank with.

A tank of this size is going to last longer than a 5 or 10 lb tank, but it can still run out surprisingly quickly if it is being used for industrial or high-energy purposes.

On the other hand, choosing a 40 lb tank can be complete overkill for a casual camping trip. To get a frame of reference, we can look at some common applications.

The average camper will only use around ½ lb of propane per day, whereas a medium-sized grill uses around one pound of propane every hour.

For larger, commercial grills you might be using two pounds of propane each hour and to heat a home that number jumps up to an hourly use of around one gallon.

A 40 lb propane tank, then, will last for around:

  • Home Heating: 10 hours
  • Large Grill: 20 hours
  • Patio Heater: 20 hours
  • RV Furnace: 30 hours
  • Medium Grill: 40 hours
  • General Camping: 80 days

What Are BTUs?

Ultimately, each appliance will burn fuel at a different rate, so you need to look at the BTU usage to see exactly how long your propane will last.

You will see the term “BTU” often when you’re looking at fuel and appliances that are powered by fuel.

BTU stands for British Thermal Units and it is a measurement of how much energy it takes to heat something up and, therefore, how much heating energy a fuel source can put out.

One BTU is the amount of energy that is required to raise the temperature of a single pound of water by just one degree Fahrenheit. Fuel sources all put out different BTUs per hour because they release different amounts of energy.

Different appliances also have different hourly BTU usages, which refers to how much heating energy they need when they are powered.

How Many BTUs Are in a 40 lb Tank of Propane?

Propane outputs 21,600 BTUs per pound per hour, which is the amount of heat energy that is provided by this fuel source. Other fuel sources output more or less energy per hour. Coal, for example, only provides around 12,500 BTUs.

A 40 lb tank of propane contains around 864,000 BTUs. You can use this number to figure out exactly how quickly your tank will be used up by any single appliance.

All propane-fuelled appliances have a BTU number of their own which will tell you how many BTUs they will use up in an hour.

A 40,000 BTU patio heater, for example, uses 40,000 BTUs every hour. To work out how many hours your 40 lb tank will last with this heater, you just divide the total BTUs by how much will be consumed every hour.

864,000 divided by 40,000 equals 21.6. Therefore, a 40 lb propane tank will power a 40,000 BTU heater for 21.6 hours.

What Do You Do When A 40 lb Propane Tank Runs Out?

When you do get to the end of your tank, there are a few different options that you have. You could purchase a whole new tank, but it is much better to take it to a filling station for an exchange or to get it refilled.

In most instances, it is much cheaper and more efficient to refill your tank rather than exchanging it for a full one.

The average cost of exchanging a propane tank is around $5.00 to $6.00 per gallon of propane but it usually only costs about $3.00 to $4.00 per gallon for a refill.

With a 40 lb tank, you will also need to consider transportation as they can be difficult to lift when full. Some RV owners use 40 lb tanks but don’t top them up all the way, so they are easier to carry around.

Read also: How To Store Propane Tanks In Hot Weather: Storage Safety Tips

Where Can You Refill a 40 lb Propane Tank?

40 lb propane tanks have the same adaptors as the more common 20 lb size so they can be topped up at any location that offers propane refilling services.

You can get your tank refilled at many different hardware stores, vehicle repair and maintenance shops, camping supply retailers, and gas stations.

There are also dedicated propane refilling locations around the country, like those run by AmeriGas, that specialise in propane services.

The largest network of refilling stations, however, are those run by U-Haul. There are more than 1,100 U-Haul propane refilling locations all over the country, so they are pretty easy to find, no matter where you are.

Read also: Blue Rhino Propane Refill Near Me (Cost, Exchange, Coupon, Walmart, Home Depot)

How Do You Know How Much Propane Is Left in a 40 lb Tank?

With a 40 lb tank, it can be very difficult to keep track of how much propane you have used, so it is easiest to weigh your tank to find out how much is left inside.

To determine how much propane you have left in your tank:

  1. Find the tare weight (TW) on the tank to identify how much it would weigh if it was empty.
  2. Place your tank on a set of bathroom scales (with a maximum capacity of over 100 lbs) to determine the current total weight of the tank.
  3. Subtract the empty tank weight from the total weight to find out how many pounds of propane you have left.
  4. You can then multiply the propane weight in pounds by 21,600 to find out how many BTUs of fuel you have remaining.

For example, if your tank has a TW of 32 lbs and a current total weight of 45 lbs. 45 lbs – 32 lbs = 13 lbs of fuel left in the tank. 13 lbs X 21,600 = 280,800 BTUs of fuel remaining.


On average, a 40 lb tank of propane contains around 9.2 – 9.4 gallons of fuel. This is the equivalent of about 864,000 BTUs.

This size of tank is quite heavy when it is full, but it lasts a decent amount of time when powering larger appliances and commercial equipment.

Though it may be overkill for a lot of smaller appliances and general usage, a 40 lb tank may be just what you need for a large outdoor space heater or a big commercial grill.


Mike Gilmour

Hi, I'm Mike, co-founder, and editor of RV and Playa. My passion is traveling (with my RV) and enjoying the day at the beach (Playa)! Well, I originally created this blog as a way to share what I've learned by experimenting with the RV lifestyle, and I want to help others develop in life through new skills and opportunities.

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