Size of 20 Pound Propane Tank | Standard Grill Cylinder Dimensions

A standard 20 lb propane tank stands about 18 inches tall and 12 inches in diameter, holding roughly 4.6 gallons of fuel when full.

The “20 pound” label on the familiar grill cylinder refers to the weight of the propane it safely holds, not the weight of the empty tank itself. That distinction trips up plenty of first-time buyers, and it’s worth understanding before you haul one home or build a storage spot around it.

The physical dimensions of a 20 lb propane tank are consistent enough that most grill carts, covers, and cylinder holders are built to fit them. The tank is the standard portable cylinder used across the United States for gas grills, patio heaters, and portable generators, and a full one weighs close to 40 pounds depending on the tare weight stamped on the collar.

What Are The Exact Dimensions?

Manufacturers vary slightly, but the measurements all land within about half an inch of each other. AmeriGas lists the standard 20 lb cylinder at 1 foot 6 inches high and 1 foot in diameter, which works out to 18 inches by 12 inches.

Other spec sheets come in close to that. Common published figures include:

• 17.8 inches high × 12.3 inches diameter
• 17-5/8 inches high × 12-1/8 inches diameter
• 18 inches high × 12.4–12.5 inches diameter

Why Is It Called “20 lb” When It Weighs More?

The number describes the propane capacity, not the total package. A 20 lb cylinder safely holds 20 pounds of propane by weight, which equates to roughly 4.6 to 4.7 gallons depending on the source. The empty cylinder, valve, and fittings add their own weight, which is why a full tank tips the scale near 40 pounds.

That empty weight is called the tare weight, and it’s a number you should know.

So when you lift a tank and wonder why 20 pounds feels like twice that, the math checks out. The propane is the 20-pound portion; the steel container carries the rest.

Filling And Overfill Rules Worth Knowing

Overfilling a 20 lb cylinder is both illegal and unsafe, and NIST’s guidance on fill verification is straightforward. The fill level is checked one of two ways: by weighing the cylinder or by using the bleeder valve method. The two methods are not used together, and a certified fill station will follow the proper procedure for the equipment it uses.

Your tank’s tare weight matters at the fill station because it’s the baseline for the weigh method. The attendant weighs the empty tank, adds the 20-pound propane allowance, and fills until the scale hits the target. If you’re replacing a tank rather than refilling, you can swap the empty cylinder for a pre-filled one at most hardware stores and gas stations.

One practical consideration: the 18-inch height and 12-inch diameter determine what kind of propane tank cover fits your cylinder and what storage space it needs. Most covers are sized for these standard dimensions, so double-check your tank’s exact measurements before ordering one, especially if you have a horizontal or specialty cylinder variant.

Does The Label Ever Mean Something Else?

The “20 lb” convention is so standard that it’s easy to assume every tank labeled that way is the same upright cylinder. That’s mostly true, but there are product variants worth knowing about. Some listings show horizontal 20 lb cylinders with valves and gauges, and those have a different shape entirely even though they hold the same propane weight.

If you’re measuring a storage area or buying a cart, use the dimensions, not the label. And if you’re comparing tanks, check the tare weight stamped on the collar so you know what you’re lifting when the tank is full.