Determining how many gallons does a 100 lb propane tank hold is ** dead simple**. You just have to follow two rules. That’s it. If you know these two rules, you don’t only know how to calculate how many gallons of propane are in a 100 lb tank; you will be able to figure out the gallons of propane any propane tank contains.

Here are two rules you have to know:

**80% propane tank rule.**Namely, every propane tank is filled up to 80% of its total capacity. Example: A 100 lb tank doesn’t hold 100 lb of propane. Rather, it contains 80 lb of propane. This is a safety requirement.**How much does a gallon of propane weigh in pounds (lb)?**Propane density depends on temperature: at 90°F, a gallon of propane weighs 4.05 lb, and at 60°F a gallon of propane weighs 4.20 lb. You can consult how much propane weighs here.

When calculating how many gallons of propane are in a 100 lb tank, we usually take the median propane density of ** 4.11 lb/gallon** (measured at 77°F).

Here is how much propane a 100 lb tank holds:

## How Many Gallons Of Propane Are In A 100 Pound Propane Tank?

We use the **1st rule**:

A full 100 lb propane tank holds 80 lb of propane.

Now, we use the **2nd rule**:

1 gallon of propane weighs 4.11 lb per gallon.

Let’s calculate how many gallons does a 100 lb propane tank hold like this:

**Gallons Of Propane = Weight Of Propane / Propane Density**

In the case of a 100 lb tank, this means:

**Gallons Of Propane **= 80 lb / 4.11 lb/gallon =** 19.46 Gallons**

Here you have it:

A 100 lb tank holds **19.46 gallons of propane**.

Using this simple calculation, you can determine how many gallons of propane are in pretty much any propane tank.

Also be aware that if you will your propane tank at lower temperatures, you will get different results of how many gallons of propane you can put in a 100 lb tank (due to different propane densities):

- If you fill a 100 lb propane tank at 60°F, it will hold
**19.05 gallons**of propane. - If you fill a 100 lb propane tank at 77°F, it will hold
**19.46 gallons**of propane. - If you fill a 100 lb propane tank at 90°F, it will hold
**19.75 gallons**of propane.

As you can see, the higher the temperature, the more propane you can put into the tank since the propane density is lower at higher temperatures.

We hope this illustrates what amount of gallons can go into a 100 lb propane tank. If you have any questions regarding this, you can use the comments below and we’ll try to help you out.