How Many Gallons Are in A Propane Tank?

How many gallons are in a propane tank

Propane is a versatile fuel used for various purposes such as heating, cooking, and powering vehicles. Understanding the capacity of your propane tank is essential for safe and efficient usage. But as you’re probably aware, propane is sold in tanks and measured by weight, so how many gallons of liquid propane do you actually get?

A gallon of propane weighs about 4.23 pounds, so:

  • 15 pounds = 3.55 gallons
  • 20 pounds = 4.73 gallons
  • 30 pounds = 7.09 gallons
  • 40 pounds = 9.46 gallons
  • 100 pounds = 23.64 gallons
  • 250 pounds = 59.10 gallons

These figures do not account for the weight of the propane tank.

In this guide, we will explore the different sizes of propane tanks, learn how to calculate the number of gallons in a tank and answer some frequently asked questions.

What Is Propane?

Propane Tank

Propane is a hydrocarbon gas that is commonly used as a fuel source. It is a byproduct of natural gas processing and petroleum refining. Propane is usually stored as a liquid under pressure and vaporizes when released, making it an efficient fuel for various applications.

Propane Tank Sizes and Uses

Propane tanks come in various sizes, ranging from small portable cylinders to large stationary tanks. They are classified by their weight in pounds and are typically used for different applications. Here are some common propane tank sizes and their uses:

  • 15lbs—Portable heaters, camping, and small appliances
  • 20lbs—Gas grills, patio heaters, and RVs
  • 30lbs—Larger BBQ grills, motorhomes, and food trucks
  • 40lbs—Residential heating, large outdoor appliances, and generators
  • 100lbs—Commercial heating, large appliances, and industrial applications
  • 250lbs—Whole-home heating, commercial, and agricultural use

Gallons in Propane Tanks

Gallons in Propane Tanks

To calculate the number of gallons in a propane tank, you need to understand the relationship between pounds and gallons. 1 gallon of propane weighs approximately 4.23 pounds. To convert the weight of the propane tank to gallons, divide the weight of the tank (in pounds) by the weight of one gallon of propane (4.23 pounds).

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To put it simply, the formula for calculating propane in gallons based on weight is as follows:

Gallons = Weight of Propane Tank (lbs.) ÷ 4.23

Calculating Gallons for Different Tank Sizes

Using the formula above, let’s calculate the number of gallons in various propane tank sizes:

  • 15lbs—15 ÷ 4.23 = 3.55 gallons
  • 20lbs—20 ÷ 4.23 = 4.73 gallons
  • 30lbs—30 ÷ 4.23 = 7.09 gallons
  • 40lbs—40 ÷ 4.23 = 9.46 gallons
  • 100lbs—100 ÷ 4.25 = 23.64 gallons
  • 250lbs—250 ÷ 4.23 = 59.10 gallons

Keep in mind that these calculations give the approximate number of gallons in each tank. Actual capacities may vary slightly depending on the manufacturer and tank design. It’s also important to note that propane tanks are not filled to their maximum capacity to allow for expansion during temperature changes. Typically, propane tanks are filled to 80% of their total capacity.

How Long Does a Gallon of Propane Last?

How Long Does a Gallon of Propane Last

The duration of a gallon of propane depends on various factors, such as the type of appliance, its energy efficiency, and the intensity at which it’s being used. To give you a better idea of how long a gallon of propane might last, let’s consider some common scenarios:

1. Grill

A standard propane grill typically uses around 20,000 BTUs (British Thermal Units) per hour. Given that one gallon of propane contains approximately 91,500 BTUs, a gallon of propane could last for around 4.5 hours of continuous grilling.

2. Space heater

A propane space heater with a 30,000 BTU output would use a gallon of propane in approximately 3 hours. However, most space heaters are not used continuously, so a gallon of propane might last for several days or even weeks, depending on usage patterns.

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3. Generator

A 5,000-watt propane generator consumes about 0.8 gallons of propane per hour at full capacity. In this case, a gallon of propane would last for about 1.25 hours.

4. Water heater

A standard tankless propane water heater with a 120,000 BTU output would consume a gallon of propane in approximately 45 minutes of continuous use. However, water heaters are not used continuously throughout the day, so a gallon of propane could last for several days, depending on the frequency and duration of hot water usage.

5. Firepit

A fire pit with an output of 40,000 BTUs would use a gallon of propane in approximately 2.3 hours. The duration will depend on how long and how often you use the fire pit.

6. Patio heater

A patio heater with an output of 46,000 BTUs would consume a gallon of propane in about 2 hours. The actual duration will depend on how often and how long you use the patio heater.

7. Pool heater

Pool heaters have varying BTU outputs, but let’s consider a pool heater with an output of 150,000 BTUs. In this case, a gallon of propane would last for roughly 36 minutes. However, pool heaters are typically not used continuously and have thermostats that control their usage. Therefore, a gallon of propane could last several days, depending on the pool’s size, temperature settings, and usage patterns.


1. How do I know when my propane tank is empty?

You can check the level of propane in your tank using a few methods. One simple method is the “water trick.” Pour warm water over the side of the tank and then run your hand along the surface. The area where the propane level is will feel colder than the empty part of the tank. Alternatively, you can use a propane tank gauge, which gives you a more accurate reading of the propane level.

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2. Can I refill my propane tank, or do I need to exchange it?

Most propane tanks can be refilled, but it’s essential to check for any damage or signs of wear before doing so. Propane tank exchanges are also available at many retail locations. When using an exchange program, you’ll receive a pre-filled tank in exchange for your empty one. This can be a convenient option, but refilling your tank is usually more cost-effective.

3. How should I store my propane tank?

Store your propane tank in a cool, dry, and well-ventilated area, preferably outdoors. Keep it away from heat sources, open flames, and direct sunlight. Make sure to place the tank on a stable and flat surface to prevent it from falling over. Always store propane tanks in an upright position.

4. How long does propane last in a tank?

Propane itself does not have an expiration date, but the tank does. A propane tank typically has a lifespan of 30 years, but it should be inspected and requalified after 10 years or so. If a tank passes the inspection, it can be used for an additional five years before needing requalification again. As long as the tank is in good condition and properly stored, the propane inside should remain usable.

5. What should I do if I smell gas or suspect a propane leak?

If you suspect a propane leak, follow these steps:

  1. Turn off the gas supply by closing the valve on the propane tank.
  2. Extinguish any open flames and avoid using any electrical devices, including light switches and phones, as they may ignite the gas.
  3. Evacuate the area immediately and ensure everyone is at a safe distance from the suspected leak.
  4. Call your propane supplier or the fire department for assistance.

Baron Cooke has been writing and editing for 7 years. He grew up with an aptitude for geometry, statistics, and dimensions. He has a BA in construction management and also has studied civil infrastructure, engineering, and measurements. He is the head writer of

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