If you’re familiar with the type of content that we like to produce, you know that we enjoy answering these types of questions. For the most part, they’re mostly dynamic and can have a multitude of different answers. Here’s the thing about the question, “How much does a gallon of propane weigh,” it actually only has one answer.

“So…then answer the question so I can move on with my life.” Yes, we know, the internet is notorious for dragging out questions until the very end when all readers want is just a simple answer to the question. In the interest of fairness, we’re going to attempt to satisfy all parties involved here by answering the question right away, but by also talking about some additional information that can be very beneficial for propane owners of any kind.

How much does a gallon of propane weigh?

A gallon of propane weighs roughly around 4.2 pounds. The answer may be different down to the decimal depending on where you look, but it’s right around 4.2 pounds regardless. See, we promised, and we delivered. It’s really that simple…that’s the coveted answer that you came here looking for.

However, this topic can be assessed a little bit further. For starters, how do you even convert gallons to pounds, anyway? No, you can’t convert gallons to pounds directly without any other variables. So, just because propane weighs 4.2 pounds per gallon, that’s not going to be the case for other liquids, gasses, or even foods.

In fact, there’s actually a formula that can help determine the conversion. Good ol’ math, right? The formula goes pounds equals gallons multiplied by 8.345404 multiplied by ingredient density. If all that sounds like gibberish to you, don’t worry, it kind of does to us too.

Essentially, all that’s being done is the density of the ingredient or material in question is being multiplied by the volume by 8.345404. Thankfully, the internet exists to make tasks like this simpler. So, if you ever want to convert gallons to pounds for anything besides propane, use this calculator.

How much do propane tanks even hold?

How much does a gallon of propane weigh? “Wait, why are you asking that again when it’s already been answered?” We ask it again because knowing that a gallon of propane weighs 4.2 pounds can have its advantages. After all, the most common way that propane is measured is via gallons, but it can also be measured in pounds.

So, knowing this number can allow you to have a better understanding of the capacity of your propane tank. Speaking of such, how much propane do propane tanks even hold? Well, propane tanks have water capacity volumes, and each tank will be filled up roughly to 80 percent of that volume. The additional space is left purposely inside the tanks to allow propane (which is stored in a liquid state) room to expand into a vapor.

As for how much propane they can hold, it can vary quite a bit. Smaller tanks could only hold around three gallons, while much larger tanks could hold up to 800 gallons (after factoring tank water capacity).

Okay…so why is all of this even important?

The money question (how much does a gallon of propane weigh) has already been answered, but there’s another important question that needs to be answered. Why is all of this even important? It’s not as if the only reason you needed to know the answer to that question was to impress your family and friends when providing them with random facts, right?

Correct. While it’s never a bad thing to be able to impress someone with your knowledge, knowing the simple number of 4.2 pounds (which equals a gallon of propane) can actually allow you to figure out how much propane is currently in your tank.

Now, with larger tanks that already have fuel gauges built-in, this is kind of pointless as you can just read the gauges to figure out the amount of propane present. Yet, smaller tanks are probably not going to have fuel gauges making it harder to find out.

Weighing propane tanks

Yep, who would’ve known that the easiest way to gauge how much propane is left is to just measure the tank? However, what about the weight of the tank itself? Doesn’t that have to be considered? Indeed, young one, it does, and that’s where tare weight comes into play.

Propane tanks will come with stamps on the collar that displays their respective tare weight (also known as TW). This number simply provides the weight of the tank when empty. So, using a weight scale, you can weigh your propane tank and take the reading you get and subtract it from the TW. Basically, the formula would be X (referring to the combined weight of the propane itself and the tank) minus TW equals Y (referring to the weight of the gas itself).

Doing this, basically, allows you to know how much propane is actually left in the tank. You’ll get a measurement in pounds and now that you know that there are 4.2 pounds in a gallon of propane, you can then figure out how many gallons of propane you have left. To do this, it would be another simple mathematical formula where you take Y (from the formula above) and divide it by 4,2.

Final thoughts

Is it just us or did this entire article feel like a math lecture? When they told us that math would be useful in the everyday world, they weren’t kidding. It’s amazing what you can do by simply knowing that there are 4.2 pounds in a gallon of propane.

If you’re looking for a new propane generator, we’ve written a pretty in-depth article on that exact topic: 5 Best & Most Efficient Propane Generators (in 2022).