The standard “20-pound” propane tank is the common portable container used for gas grills, outdoor heaters, and recreational vehicles. The “20 pounds” designation refers strictly to the maximum weight of the propane fuel the tank is designed to hold, not the total weight of the cylinder itself. The weight of the empty tank, known as the Tare Weight, must be added to the fuel weight to determine the total weight when full. This difference is important for safe handling, transportation, and the accurate refilling of the tank.
The Standard Tare Weight
The empty weight of a standard 20-pound propane cylinder, officially called the Tare Weight (TW), typically falls within a range of 17 to 20 pounds. This empty shell weight is almost as much as the propane it contains. Manufacturers use different steel alloys, construction methods, and valve types, which results in slight variations between tanks.
Tanks made primarily from steel generally occupy the higher end of this weight range. Less common aluminum tanks can be lighter. The total weight of the empty tank includes the cylinder body, the protective collar, and the necessary valves and fittings.
Decoding Tank Markings
To find the exact empty weight, consumers should look for markings stamped into the metal collar or handle at the top of the tank. The most important marking is “TW,” which stands for Tare Weight, followed by a number representing the precise weight of the empty tank in pounds. This number is determined at the time of manufacture and is the definitive weight used by licensed refill stations.
Another marking is “WC,” which denotes the Water Capacity of the cylinder in pounds. This number indicates the weight of water the tank could hold if completely full. Regulators use this capacity to calculate the maximum safe fill volume for propane, which is limited to 42% of the water capacity by weight to allow for liquid expansion. The collar also includes the original manufacturing date, which tracks the cylinder’s required re-certification schedule.
Full Weight and Practical Use
The total weight of a fully filled 20-pound propane tank is calculated by adding the stamped Tare Weight (TW) to the 20 pounds of propane it holds. For example, a tank with a common TW of 17 pounds weighs approximately 37 pounds when full. This total weight is relevant for safe lifting and handling, as the weight more than doubles when the tank is filled.
Knowing the empty weight also allows users to check the fuel level without a gauge. By placing the tank on a scale and subtracting the stamped TW, the remaining weight of the propane can be determined. This calculation is important for refill services, as the attendant uses the TW to ensure they dispense the precise 20 pounds of propane by weight. Tank exchange services often do not require the TW because they typically only fill tanks to 15 pounds.