Propane Usage & Tank Size Calculator – How Long Will Your Tank Last?

propane usage and tank size calculator

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How long will a 20 lb. propane tank run a grill? How long will it run a fire pit? What about a 30 lb. tank or one of those disposable green 1 lb canisters?   Use our propane usage and tank size calculators to find out!

When we started RVing, propane was one of the most confusing things for me to wrap my head around.  How big is my tank?  30 lbs.  Great.  Then I get it refilled and they tell me it holds about 7 gallons of propane.  Wait what?  How long will my tank run my fire pit?  Oh, for that you need to know the BTU rating of your fire pit.  Yeah.  

Well, we recently got a new fire pit and while figuring out how long it would run on various propane tanks, I decided it would be easier to use a calculator to find the answer.  So I made one. I’m not a propane expert, just someone who likes math and uses propane.

There are two basic types of propane tanks. Portable tanks (DOT cylinders) and ASME tanks. ASME tanks are permanently installed, and usually larger, you might see them at a gas station or in a motorhome. Portable propane tanks are smaller- these are the tanks commonly used for a BBQ grill, travel trailer or fifth wheel . For the purposes of this article, propane tank refers to a DOT propane cylinder.

How much propane does a 20 lb propane tank actually hold when filled?

There is a lot of confusion about this because propane tanks can only be filled to 80%. This is for safety – so that there is room for expansion. In fact, propane tanks are equipped with an OPD (Overfill Prevention Device) that prevents the tank from being more than 80% filled.

A 20 pound propane tank is designed to hold about 20 pounds or 4.7 gallons of propane. This accounts for the fact that the tank can only be filled to 80%.  In other words, when you fill a 20 pound propane tank to 80%, it holds about 20 pounds (4.7 gallons) of propane.

The two questions about propane that I hear again and again are:

How long will my grill, fire pit, patio heater, camp stove run on a tank of propane?
Jump to the PROPANE USAGE CALCULATOR to estimate how long your DOT propane tank will run your appliances.

How much propane is really in my DOT propane tank when it is filled?
Size in pounds.
How many gallons your tank will hold when filled.
How many BTU it will produce.

propane usage calculator

How to use the calculator to find out how long your portable propane tank will run a propane appliance.

You’ll need to know two things:

  1. The size of your propane in tank pounds
    • If you don’t know what size your tank is, you can use the propane tank size calculator at the bottom of the page to find out.
    • Propane tank exchanges only fill the tanks to 15 pounds. They should say this right on the front.
  2. The BTU rating of your appliance.
    • Most propane appliances have their BTU rating either on a sticker or stamped somewhere. If you can not find it you should be able to look it up in the user manual or the manufacturer’s website.

A few examples for reference:
The Outland 870 Firebowl BTU rating is 58000. If you use it on high with a 20 lb. propane tank, it should run for about 7.4 hours. Of course, if you turn it down a little it will run longer.

Our Weber Q 1000 has a BTU rating of 8500. We use it with a 4.25 lb. tank and it runs for about 10.8 hours on high. (This is a great size for an RVer, it’s one of my favorite upgrades. Check out our Worthington 4.25 lb Portable Propane Tank Review for details. )

The BTU rating tells you how much energy like a propane fire pit can put out so the result of the calculator will tell you how long your device will run on its highest setting.

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Propane Usage Calculator - How Long Will My Propane Tank Last?
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Propane usage and efficiency varies based on things like temperature so while this calculator can give you a very good idea of how long your tank will last, it won’t be exact. It is based on usage at 60 degrees Fahrenheit. For example, if it is very cold out your propane will not last as long.

Our Top Pick for an RV or Grill Propane Tank Gauge

See accurate readings of your remaining propane via an app on your phone or the LED display!

The Ultrasonic Propane Level Gauge with Bluetooth – 2 Sensor & LED Monitor Kit is great for RV applications. Depending on how your tanks are mounted, you may also want a snap on tank riser or halo.

Single Ultrasonic Propane Level Gauge Sensor works well for a grill propane tank.

RV Appliance Propane Usage

While you can use the usage calculator to estimate how long your RV furnace, refrigerator or oven will run, you will really only get a ballpark idea of how long your propane will last in real life. There are a few reasons for this. First, how much propane an appliance uses varies based on things like temperature. If it is very cold out, your propane will not last as long.

Second, these appliances do not run all the time. Your furnace, for example, only comes on when it needs to, so you would also need to estimate how much time it is actually running. Of course, that in and of itself is difficult because the colder it is outside, the more the furnace needs to run.

Third, in an RV you are running all of your propane appliances from the same tank so you’ll need to account for how long each one runs and how much propane it uses.

Also, regarding an RV furnace and refrigerator, don’t forget that they use electricity too. Even when running on propane. Make sure to account for your batteries.

Not sure what size your tank is?

Portable propane tank sizes you’ll find for RV camping commonly range from 1 lb to 40 lbs. The small green disposable canisters are 1 lb. tanks. Next up are 4 lb. to 5 lb. tanks and 11 lb. tanks – these are small refillable tanks that are great for an RV campsite grill.

Standard BBQ tanks are 20 lbs. – these are the ones you see at propane exchanges at grocery and hardware stores. Travel trailers usually have 30 lb. tanks although sometimes they use the 20 lb. tanks. (The 30 lb. tanks are about 24 inches tall and the 20 lb. tanks are about 18 inches tall.) Some fifth wheels use 40 lb. tanks and these are usually about 29 inches tall.

Propane tank size calculator

Find out how many pounds your propane tank is and how many gallons of propane it will hold when filled.

You need one number: The water capacity of your propane tank. (WC)

  • Take a look at the collar of the tank.  You will see that there is quite a lot of information stamped into the collar.  
  • Look for WC.  This is the water capacity of your tank. 
  • Multiply your WC by .42 to find out how many pounds of propane your tank will hold. Or just enter it in the calculator.

Let’s say your propane tank has 47.6 lbs stamped on the collar next to WC.
47.6 x .42 = 19.99 so you have a 20 lb. propane tank!
When filled to 80% it will hold 20 pounds or 4.72 gallons of propane.

A note about propane tank exchanges: Although they use 20 lb. tanks, they only fill them to 15 pounds. Look at the label to verify. If you want to know how many gallons or BTU for a tank exchange tank enter 35.71 for WC to approximate 15 pounds.

This calculator is for educational purposes only. Propane tanks should only be filled by licensed refilling stations in accordance with local regulations.

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What size is my propane tank and how many BTU will it produce?
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Propane volume, usage and efficiency varies based on things like temperature so while this calculator can give you a very good idea of how much propane your tank will hold, and how many BTU it will produce, it won’t be exact. It is based on usage at 60 degrees Fahrenheit.

Hope you enjoyed the calculators! I had fun making them.

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