Propane tanks are portable storage containers that hold and transport propane gas. Propane gas is generally expressed in gallons and propane tanks can hold a specified maximum number of gallons of propane gas when full. If the tank does not have a built-in gauge, it is difficult to determine how many gallons of propane gas the tank currently has. You can, however, manually calculate the gallons of propane gas currently in the tank.
Examine the propane tank and find it tare weight (TW). The TW is the weight of the tank when empty. You can normally find this information on the tank's label or engraved on the bottom of the tank. For example, assume a propane tank has a TW of 8 lbs.
Determine the current weight of the propane tank. Plac it on the scale and read the scale's display to determine the current weight. For example assume the current weight of the propane tank is 24 lbs.
Calculate the weight of the propane currently in the tank by subtracting the TW from the current weight of the tank. Continuing the same example 24 - 8 = 16 lbs.
Divide the current weight figure from Step 3 by 4.23. The weight of propane is 4.23 lbs. per gallon. Continuing the same example, 16 / 4.23 = 3.78. This figure represents the number of gallons of propane currently in the tank.