Propane Tank Size Converter
Convert propane tank sizes — weight (lbs), capacity (gallons), BTU energy, and standard tank names.
Plan refills for grills, generators, home.
Type in any field — the others update instantly. All conversions reference liquid propane at 60°F.
Propane is sold by weight, used by volume, and stored in tanks measured both ways. That mismatch causes endless confusion — a “20 lb” BBQ tank holds about 4.7 gallons, weighs roughly 38 lbs when full, and contains around 430,000 BTU of energy. Different number for the same physical object, depending on who’s asking.
The basic conversions (propane at 60°F):
| From | Multiplier | To |
|---|---|---|
| 1 lb propane | × 0.2362 | gallons |
| 1 gallon propane | × 4.234 | lbs |
| 1 gallon propane | × 91,502 | BTU |
| 1 lb propane | × 21,591 | BTU |
| 1 lb propane | × 6.33 | kWh |
| 1 gallon propane | × 26.82 | kWh |
These numbers all reference liquid propane at room temperature. Propane is stored as a liquid in tanks but is used as a gas — the vaporization happens inside the tank as gas is drawn off the top.
Standard tank sizes:
| Name | Water capacity | Propane (80% fill) | Empty tank weight | Full weight |
|---|---|---|---|---|
| 1 lb (camping) | 1 lb | ~1 lb / 0.24 gal | 0.6 lb | 1.6 lb |
| 11 lb (small) | 11 lb | ~11 lb / 2.6 gal | 9 lb | 20 lb |
| 20 lb (BBQ standard) | 24 lb water | ~20 lb / 4.7 gal | 17 lb | 38 lb |
| 30 lb (large grill / RV) | 36 lb water | ~30 lb / 7.1 gal | 24 lb | 54 lb |
| 33 lb (forklift) | 40 lb water | ~33 lb / 7.8 gal | 27 lb | 60 lb |
| 40 lb (commercial) | 48 lb water | ~40 lb / 9.4 gal | 33 lb | 73 lb |
| 100 lb (residential) | 120 lb water | ~100 lb / 23.6 gal | 70 lb | 170 lb |
| 120 gallon (home tank) | 120 gal water | 96 gal / ~408 lb | 322 lb | 730 lb |
| 250 gallon (home tank) | 250 gal water | 200 gal / ~850 lb | 480 lb | 1,330 lb |
| 500 gallon (home tank) | 500 gal water | 400 gal / ~1,700 lb | 950 lb | 2,650 lb |
| 1,000 gallon (home / farm) | 1,000 gal water | 800 gal / ~3,400 lb | 1,790 lb | 5,190 lb |
The 80% fill rule. Propane tanks are filled to 80% of water capacity to leave room for thermal expansion of the liquid. As temperature rises from 70°F to 120°F, propane volume increases by roughly 6%. Tanks filled to capacity (above 80%) can vent at the pressure-relief valve in summer heat — a frequent source of garage and RV propane fires.
Reading a tank label.
US propane tanks are stamped with three key markings:
- WC (Water Capacity): the total volume in pounds of water
- TW (Tare Weight): the empty weight of the tank
- DOT/TC number: the manufacturer/inspector code
The propane capacity is approximately 80% of WC (in pounds of water, propane is about 0.504 times as dense, so 80% × 0.504 ≈ 0.42 × WC in pounds of propane).
Tank recertification.
US propane tanks require recertification 12 years from manufacture, then every 5 years after. Look for the date stamp on the collar — uncertified tanks cannot be filled by most refill stations.
Refill economics.
Refilling at a propane filler station (Tractor Supply, U-Haul, hardware stores) costs about half what a tank swap costs. A 20 lb tank refill runs $15-25 USD; a tank swap (Blue Rhino, AmeriGas exchange) runs $25-40 and usually shorts you about 5 lb of propane — the exchange tanks are filled to 15 lb of propane, not the 20 lb a full refill provides.
Approximate runtime by appliance:
| Appliance | BTU/hr | Hours from 20 lb tank | Hours from 100 lb tank |
|---|---|---|---|
| Patio heater | 40,000 | 11 | 54 |
| BBQ grill (3 burners) | 30,000 | 14 | 72 |
| Camping stove (2 burners) | 18,000 | 24 | 120 |
| Tankless water heater | 199,000 | 2 | 11 |
| Furnace | 100,000 | 4 | 22 |
| Generator (7 kW) | 95,000 | 4 | 23 |
| Fireplace insert | 30,000 | 14 | 72 |
These are full-output hours — real-world use is usually intermittent so practical runtime is longer.
Choosing a tank size. For occasional grilling, a 20 lb tank is fine. For a generator backup, get a 100 lb tank or larger — refilling generators during a power outage is annoying. For whole-home heating, you need a permanent 250-1,000 gallon tank installed by a licensed propane service.
Cold weather and propane.
At low temperatures, propane vaporization slows. A tank in 0°F weather may not deliver enough gas pressure to run a high-BTU appliance. Larger tanks have more surface area and vaporize faster; small bottles can frost over and starve appliances of fuel. Below 20°F, plan to use larger tanks or to keep small tanks insulated.