How long a 40 lb propane tank lasts, by appliance
This is a large cylinder for RVs, fish fryers and heaters. It holds about 9.4 gallons of propane, which is 862,845 BTU. Runtimes are for the appliance running continuously, at full power and at 70% of its rating, with no refills.
| Appliance | BTU/hr | At full power | At 70% power |
|---|---|---|---|
| Gas grill, 2-burner | 24,000 | 36.0 h | 51.4 h |
| Gas grill, 3-burner | 36,000 | 24.0 h | 34.2 h |
| Patio heater | 40,000 | 21.6 h | 30.8 h |
| RV furnace | 30,000 | 28.8 h | 41.1 h |
| Tank water heater | 40,000 | 21.6 h | 30.8 h |
| Fire pit | 50,000 | 17.3 h | 24.7 h |
| Gas range (everything on, max) | 65,000 | 13.3 h | 19.0 h |
| Whole-house furnace | 80,000 | 10.8 h | 15.4 h |
| Tankless water heater | 150,000 | 5.8 h | 8.2 h |
Tips and safety
Weigh the cylinder to see how much is left (subtract the tare weight stamped on the collar), keep it upright and outdoors, and never fill it above 80%. Use the propane runtime calculator for your own appliance, and see the propane tank guide for the formula and safety checklist.
Equivalents and practical notes
This tank holds the same propane as about 2.0 standard 20 lb cylinders, at 40 lb of propane.
Cylinders are refilled by weight at a propane dealer. A cylinder this size is portable.
Want to change anything else? The calculator above is the full Propane Tank Runtime Calculator: edit any number and the results update instantly.
Tools & materials for this project
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Frequently asked questions
How long does a 40 lb propane tank last on a grill?
About 24.0 h of cooking at full power on a 3-burner grill (36,000 BTU/hr), or 34.2 h at a more typical 70% of full power. A 2-burner grill (24,000 BTU/hr) gets 36.0 h at full power.
How many gallons of propane are in a 40 lb tank?
About 9.4 gallons (40 lb of propane). One gallon of propane weighs about 4.24 lb. That is 862,845 BTU of energy.
How long will a 40 lb propane tank run a furnace?
A whole-house furnace rated at 80,000 BTU/hr burning non-stop uses a 40 lb tank in about 10.8 h. A furnace cycles on and off, so a tank lasts longer in practice. Smaller or more efficient homes use less.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.