Portable propane tanks come in a variety of sizes ranging from 4 to 100 pounds. The 20-pound tank is the size most often used for gas barbecue grills. It holds 4.7 gallons of liquefied propane. Other portable sizes include the 30- and 40-pound tanks.
The size of the tank represents the approximate weight of propane it holds. The total weight of a filled tank is significantly more. For example, a 20-pound tank weighs approximately 38 pounds when full. A 100-pound tank weighs 170 pounds when full. While a larger tank increases the operating time for the appliance, it is not always practical.