Propane tanks are most commonly referred to by their water capacity volume, and propane tanks are normally filled to 80% of its water capacity. For example, a 120-gallon tank will hold approximately 100 gallons of propane when completely full. Since propane is stored in a liquid state under pressure, it needs room to expand into a vapor. This extra “room” that is in the tank allows for that expansion. Depending on the ambient temperature outside, propane may expand more or less.
Propane Tank Capacities (assuming 80% of tank water capacity)
20lb Propane Tank ~ 3.5 Propane Gallons
100lb Propane Tank ~ 24 Propane Gallons
420lb Propane Tank (120 Gallon WC) – 100 Propane Gallons
500 Gallon Propane Tank (500 Gallon WC) – 400 Propane Gallons
1,000 Gallon Propane Tank (1000 Gallon WC) – 800 Propane Gallons