How do you determine the fuel capacity of a propane tank?

Check the propane tank size on the side of the tank, or else measure its dimensions and compare to standard sizes for propane tanks. A propane tank should only be filled to 80 percent of its capacity; for example, a 5-gallon tank can only hold 4 gallons of propane.

Propane tanks are available in a wide range of sizes from the 4.7 gallon tank for a barbecue and up to 23 gallon or more tanks for heating homes or operating back up generators. However, these tanks do not always display the capacity on the side. With a tape measure, it is easy enough to compare the tank's dimensions to standard tank sizes.

1. Measure the tank height

Use a tape measure to find the height of the tank from the very bottom of the tank to just under the tank collar. This measurement should be in inches.

2. Measure the tank diameter

Wrap the tape measure around the widest point of the tank to find its diameter in inches.

3. Compare the tank dimensions to standard sizes

There are many tank sizes available, but here are the four most commonly seen and used by most tank manufacturers.

• #20: Measures 18-inches tall and 12.5-inches in diameter with a 4.7 capacity
• #30: Measures 24-inches tall and 12.5-inchs in diameter with a 7.1 gallon capacity
• #40: Measures 29-inches tall and 12.5-inches in diameter with a 9.4 gallon capacity
• #100: Measures 48-inches tall and 14.5-inches in diameter with a 23.6 gallon capacity

4. Find the fill capacity

Multiply the total tank capacity by 0.8 to find out how much propane it can safely hold. This will be an amount that is roughly 80 percent of the total tank capacity.