Propane Tank Capacity Guide (All Sizes) Gallons, Weight
It isn’t fun to run out of propane, whether grilling, camping, or running a generator. Determining the propane tank capacity is important to avoid a cold night in the RV, an unfinished brisket, or even having to close the food truck early.
Every gallon of propane weighs 4.24 lb. And one pound of propane equals 0.236 gallons of volume. To determine how much propane is left, you can subtract the TW (tare weight) of your tank from the current weight. This will give you the weight of propane in the tank.
In this article, we’ll help you understand how to calculate the amount of propane in your tank. We’ll also compare the propane capacity of common tank sizes so you can decide which size is right for you.
Propane Measurements
Propane is measured in pounds, and one pound of propane equals 0.236 gallons. To calculate the number of gallons in your tank, multiply the number of pounds of propane by 0.236.
In the US, propane is also measured in gallons. One gallon of propane equals 4.24 pounds. To calculate the number of pounds in your tank, multiply the number of gallons of propane by 4.24.
How Many Gallons of Propane in a Tank?
Here’s the full volume breakdown (gallons and liters), plus the empty and full weight of 1, 5, 20, 30, and 40 lb tanks.
| Tank Size | Volume Capacity | Volume (Metric) | Full Weight | Empty Weight |
|---|---|---|---|---|
| 1 Pound Tank | 0.236 gallons | 908 mL | 2 lb | 1 lb |
| 5 Pound Tank | 1.18 gallons | 4.47 L | 13 lb | 8.8 lb |
| 20 Pound Tank | 4.7 gallons | 17.8 L | 37 lb | 17 lb |
| 30 Pound Tank | 7 gallons | 26.5 L | 53 lb | 22.7 lb |
| 40 Pound Tank | 9.4 gallons | 35.6 L | 72 lb | 29 lb |
Why Weights Vary: 3 Reasons
As you’ll notice in the chart, the empty weight plus propane doesn’t always match the full weight. This is for three reasons.
- Tank style: Some tanks are made differently and thus have different weights. To determine the exact weight of your tank, look for the TW stamp. This is the empty weight of your tank.
- Temperature: Propane volume changes with temperature. At 60 °F (15.6 °C), a gallon of propane weighs 4.2 lb. Propane expands 1.5% per 10 °F. As the temperature increases, a gallon of propane gets lighter.
- Expansion: Tanks aren’t filled to capacity. To allow room for expansion, tanks are intentionally underfilled, often to 80% capacity. But from experience, this can vary up or down around 10%.
Propane tanks only fill to 80% capacity; this is for safety reasons in case the propane expands in warm weather. It leaves room for the propane to expand if the temperature increases.
Converting Measurements
You can use an online conversion calculator to convert between pounds and gallons. The most common residential propane tank sizes are 20, 30, and 40 pounds.
Commercial propane tanks can be much larger but are uncommon for residential and RV use.
Propane Tank Markings
Here’s what the markings on the tank mean.
- WC: Water Capacity. The water capacity of the tank, listed in pounds.
- TW: Tare Weight. The empty weight of the propane tank. Imperial measurement (pounds).
- T: Also, the Tare Weight, listed in metric (kilograms).
Here’s what they look like on my 30 lb propane tank.
How Many Gallons of Propane in a 5 lb Tank?
A full 5 lb tank of propane only contains up to 1.18 gallons of propane.
5lb tanks are quite small. These tanks are commonly used for camping or as a backup fuel source. They are not really large enough to be used as a primary fuel source.
An empty 5 lb tank weighs under 9 lb. And a full tank weighs around 13 lb.
How Many Gallons of Propane in a 20 lb Tank?
A full 20 lb propane tank contains up to 4.7 gallons of propane.
The 20 lb tank is the most common propane tank size for residential use as it is large enough to be a primary fuel source for most applications. They can fuel BBQ, generators, and camp stoves.
An empty 20 lb tank weighs 17 lb. And a full tank weighs around 37 lb.
How Many Gallons of Propane in a 30 lb Tank?
A full 30 lb propane tank contains up to 7 gallons of propane.
The size of a 30 lb tank is a workhorse and is my favorite size. I have two for our generator. They have 50% more capacity than the 20 lb but are still manageable in size.
An empty 30 lb tank weighs 22.7 lb. And a full tank weighs around 53 lb. You can find these tanks at most home and hardware stores.
How Many Gallons of Propane in a 40 lb Tank?
A full 40 lb propane tank contains up to 9.4 gallons of propane.
40 lb tanks are popular choices for commercial applications, like food trucks, commercial generators, and home RV hookups. They are also popular for RVs because they provide enough propane to power the RV’s appliances.
If you’re looking for a tank that will last longer between fill-ups, a 40 lb tank is a good option. The 40lb tank is exactly double capacity over the popular 20 lb tank. If you can handle the weight, it means you’ll have less tanks to manage.
An empty 40 lb tank weighs 29 lb. And a full tank weighs around 72 lb. These larger tanks are not standard for residential use, but they are available if you need a lot of propane capacity.
When choosing a propane tank, it’s important to consider the size of the tank and the propane capacity. The most common residential propane tank sizes are 20, 30, and 40 pounds.
Do you know: Can Propane Freeze?
Keep reading: Are Propane Heaters Safe in a Tent?
Your Turn
And that’s the answer to “How many gallons of propane in a 30 lb tank?” and other common propane tank sizes. The most common residential propane tank sizes are 20, 30, and 40 pounds. When calculating other sizes, remember that the tanks are typically filled to 80% capacity, leaving room for the propane to expand if the temperature increases.
Remember the simple conversion: one gallon of propane weighs 4.24 pounds.
Have a question about tank size and capacity? Please join me in the comment section below.
Ed … the 5lb, 20lb, 30lb listing is the absolute perfect world max amount of propane mass each tank could be filled with … typically they are only filled to 80% of that rating in order to allow for safety margin in less than ideal conditions.
Why are they called 5lb, 20lb, 30lb when those numbers have nothing to do with their full or empty weight, or weight of the propane?
I’m going to over simplify things just to make it easy. Those high school science classes that you thought were useless would help with understanding.
The TLDR; version is that the weight is the nominal weight of propane that the tank can store at 100%.
The first concept is the word “nominal”. The weights you listed are nominal weights. The easiest way to understand this is that propane tanks are not scientific devices, so they may vary in size, don’t be surprised if they vary by +/- 10%. As an example a 20 pound tank may in actuality 18 to 22 pound. 3-5% difference is more common.
The next concept that these propane tanks are called LP, which means Liquid Propane (not Low Pressure as many assume). As the temperature increases the density decreases. This is why regulations require that you only fill the tank to 80%. If you don’t give room for expansion the tank fittings can fail, which is extremely dangerous.
As you use the propane the liquid level will decrease and the “void” is filled with gaseous propane. For this reason you should try not to “empty” the tank. 20% is a good point to consider empty.
So the math is multiplied by 80% divided by 4.24 pounds per gallon (I believe at 77F/25C because that is a common temperature to use and at sea level). 25C at sea level is called “Normal Temperature and Pressure).
So a 20 pound tank at 80% full is 16 pounds. 16 pounds divided by 4.24 is 3.77 gallons at 25C at sea level.
As each tank will be up to +/- 10% different from “nominal” a 20 pound tank might be between 18 pounds and 22 pounds. 80% means 14.4 pounds to 17.6 pounds or 3.4 to 4.2 gallons, at 25C at sea level. Most propane tanks will be within 3-5% of their nominal value.
In reality most people will only deal with gallons if they pay to refill their tank at a refill station, because they charge by the gallon. If you trade in your 20 pound tank then you get charged a flat fee, but often end up with a tank filled to about 75%.
Portable propane tanks do not have a fuel gauge based on gallons. If you want to accurately know how full the tank is, weigh it and subtract the tare weight. That gives you pounds of propane.
Large tanks often have gauges in percent. If you want to know how much propane you can use, multiply percent minus 40% by tank size. Example. I have a 500 gallon tank at my house. The propane company will only fill it to a max of 80%, or 400 gallons. If the tank goes below 20% they require a safety inspection. This means I have 300 gallons usable. If my tank gauge says 50% I only have 30% usable or 150 gallons.
The only time I care about gallons is when it’s time to refill. That statement is true for my all my propane tanks: 10 pound, 20 pound, 30 pound, 40 pound and 500 gallon.
For my two RV 30 pound tank I have a remote sensor that uses sonar to determine percentage full. I then said that the capacity was 6 gallons because it’s close enough and I only care about percent. Eventually I will have the remote sensors for my other two 30 pound tanks and two 40 pound tanks which I use for a generator.
Thats how many pounds of propane fill the tanks to 80%. Used to fill them. Tank weight (Tara weight) plus pounds of propane tank is rated for( say 30 pounds )
It is based on how many pounds fit inside the tanks. So 30 pounders all have the same in them but the tanks can weigh different amounts
The numbers 5lb, 20lb, and 30lb refer to the approximate weight of the propane the tank is designed to safely hold, not the total or empty weight of the tank itself.
On the contrary, and as the article explains, the ratings relate to the weight of the propane the tank is capable of storing.