Quick answer: Enter how much propane you have, your appliance's rated fuel input and your average operating level, and this calculator estimates the maximum runtime and how many typical sessions that fuel covers. With the defaults, 20 lb at 40,000 BTU/hr gives about 10 hours 47 minutes. It is free, with no signup, and you can also try the Portable Power Station Runtime Calculator and Fence Material Calculator.
Propane Tank Burn-Time Calculator
Estimate how long your propane will last based on the fuel you have, your appliance's rated consumption, and how heavily you plan to use it.
Running a grill, heater, camping stove, generator, or other propane appliance? Enter the amount of propane available and the appliance's fuel rating to get an estimated maximum runtime. You can also estimate how many typical sessions that fuel supply could cover.
Calculate your propane runtime
Use the rating printed on your appliance or in its manual. For the most useful estimate, enter the fuel you actually have left.
At 1.5 hours per session, you have about 7.2 sessions.
How this works
The calculator converts your propane amount into an approximate amount of chemical energy, then divides that energy by the appliance's effective fuel-use rate. The base propane heat content used here is 91,452 BTU per US gallon, a current conversion factor published by the U.S. Energy Information Administration. Fuel heat content can vary somewhat with composition and location, so the result is an estimate rather than a guarantee.
Runtime = available energy ÷ (appliance BTU/hr × operating level)
When you enter propane by weight, the calculator converts the weight to an approximate US-gallon equivalent before applying the same energy factor. Metric and imperial inputs are converted in your browser; nothing is sent to a server.
Tips for getting a better estimate
- Use the appliance's rated input from its label or manual rather than guessing from its size.
- If a burner or heater cycles on and off, use a realistic average operating level instead of 100%.
- For grilling, remember that preheating and repeated opening of the lid can change actual fuel use.
- For camping or emergency planning, leave a sensible reserve rather than planning to consume the tank down to the last possible hour.
- If you have several appliances sharing one supply, calculate each appliance's consumption separately and combine their rates when they run simultaneously.
- For a purchase decision, compare the result with the manufacturer's guidance for the specific tank, appliance, regulator and operating conditions.
Honest limitations and safety
This calculator estimates fuel runtime; it does not certify safe operation.
The estimate assumes the entered propane amount is actually available for use and that the appliance consumes fuel at the selected effective rate. Real-world runtime can be shorter or longer because of cycling, heat settings, ambient temperature, wind, appliance efficiency, fuel composition and other conditions.
Do not use this calculator to determine whether a propane appliance is safe, correctly installed, properly regulated, adequately ventilated, or suitable for a particular location. Follow the appliance and tank manufacturer's instructions. Never use fuel-burning equipment indoors unless it is specifically designed and approved for that environment.
How this calculator works
The calculator turns a propane amount into energy, then divides that energy by how fast the appliance uses it. When you enter propane by weight, the tool first converts the weight to an approximate US-gallon equivalent, then applies the propane heat content of 91,452 BTU per US gallon. The appliance's effective rate is its rated input multiplied by the average operating level, because a burner that cycles off half the time uses about half its rated input on average.
Available energy = propane volume x 91,452 BTU/US gal. Effective rate = appliance BTU/hr x operating level. Runtime = available energy divided by effective rate. Dividing the runtime by the session length gives the number of typical sessions the fuel covers.
Worked example: the default setup
Use the defaults: 20 lb of propane, a rated input of 40,000 BTU/hr, an average operating level of 100%, and a session length of 1.5 hours.
- Available energy: the tool shows 431,653 BTU for 20 lb (20 lb is 9.07 kg).
- Effective rate = 40,000 x 100% = 40,000 BTU/hr.
- Runtime = 431,653 divided by 40,000 = 10.79 hours, which the tool shows as 10 hr 47 min, about 10.8 hours.
- Sessions = 10.79 divided by 1.5 = about 7.2 sessions.
That is a maximum estimate for continuous full-rate use. If the appliance cycles, set a realistic average operating level instead of 100%, and keep a reserve for camping or emergency planning rather than planning to use the last hour of fuel.
Quick reference: one 20 lb tank at 100% operating level
The table below keeps the same 431,653 BTU of available energy and only changes the appliance's rated input, so a smaller burner lasts much longer than a large one.
| Appliance rated input | Estimated runtime |
|---|---|
| 15,000 BTU/hr | About 28 hours 47 minutes |
| 30,000 BTU/hr | About 14 hours 23 minutes |
| 40,000 BTU/hr | 10 hours 47 minutes |
| 50,000 BTU/hr | About 8 hours 38 minutes |
Actual runtime varies with appliance cycling, heat setting, weather, fuel composition, and equipment condition, so treat every figure as an estimate, not a guarantee.
Frequently asked questions
How long will a 20 lb propane tank last?
It depends on the appliance's fuel consumption. For example, at 40,000 BTU/hr and continuous full output, a 20 lb propane supply provides roughly 10.8 hours of theoretical runtime using the energy assumptions in this calculator. Lower average output can extend the practical runtime.
How do I calculate propane runtime from BTU?
Convert the available propane to an energy amount, then divide by the appliance's BTU-per-hour input. If the appliance does not run continuously at full output, adjust the rate using a realistic average operating level.
Can I use this calculator with propane heaters, grills and generators?
Yes, provided you know the appliance's fuel input rating and the amount of propane available. The result is an energy-based estimate and should not replace the manufacturer's operating, ventilation or safety instructions.