RV Propane Runtime Calculator
Updated .
This estimator turns your tank size, fill level and the BTU per hour and hours per day you enter for each appliance into the days of propane remaining. It uses two approximate constants, about 91,500 BTU per US gallon and about 21,600 BTU per pound of propane. Real use shifts with cold, regulator problems and appliance cycling, so plan to swap with a margin rather than run empty.
How it works
The estimator converts propane to energy, adds up what you burn in a day, and divides:
- Propane on hand = tank capacity × fill level ÷ 100.
- Energy on hand (BTU) = propane on hand × about 21,600 BTU per pound, or × about 91,500 BTU per US gallon if you entered gallons.
- Daily use (BTU) = for each appliance, BTU per hour × hours per day burning, added together. Hours are capped at 24 a day.
- Days to your swap level = (energy on hand − energy at your swap level) ÷ daily use. Days until empty = energy on hand ÷ daily use.
The constants are approximations. Propane holds roughly 91,500 BTU per US gallon and roughly 21,600 BTU per pound; the exact figure varies a little with the gas mix and temperature. They are physical properties of the fuel, not claims about any tank or appliance. Your tank capacity, appliance ratings and hours are the figures you supply.
Why reality differs. Cold weather raises furnace and water-heater run time and can lower how much a tank delivers. A regulator that is worn or not matched to the system can change how appliances burn. Burners cycle on and off, so the hours burning are less than the hours an appliance is switched on. Use the first day or two of a trip to compare the estimate with how fast your gauge or scale reading really falls, then adjust the hours.
Swap with a margin. Appliances can quit, the furnace can lock out overnight, and a refill is not always nearby, so choose a swap level well above empty and treat the days-until-empty line as an upper limit you do not plan to reach. This tool is not a leak check or a carbon monoxide check; see the propane system checks and carbon monoxide, heat and cold exposure guides.
Worked example
Suppose a hypothetical 40 lb of propane capacity, 80% full, with a swap level of 20%. The driver enters a furnace at 20,000 BTU/hr for 6 hours, a water heater at 10,000 BTU/hr for 1.5 hours, a refrigerator at 1,000 BTU/hr for 12 hours and a range at 9,000 BTU/hr for 1 hour.
Propane on hand: 40 × 0.80 = 32 lb, which is 32 × 21,600 = 691,200 BTU. Daily use: 120,000 + 15,000 + 12,000 + 9,000 = 156,000 BTU, or about 7.2 lb. Swap-level energy: 8 lb × 21,600 = 172,800 BTU. Days to the swap level: (691,200 − 172,800) ÷ 156,000 = 3.3 days. Days until empty: 691,200 ÷ 156,000 = 4.4 days, a figure not to plan around.
Now a cold stretch: the furnace burns 10 hours instead of 6. Daily use becomes 236,000 BTU and the days to the swap level fall to 2.2. The same tank lasts a third less time on one input, which is why the furnace hours deserve the most attention. These numbers are illustrative arithmetic, not data about any tank, appliance or rig.
Frequently asked questions
Where do I find BTU per hour for my appliances?
On the appliance data plate or in its manual. Type in what it says for the burners you use. The tool does not know your equipment and has no built-in values.
Why enter hours burning instead of hours switched on?
Furnaces, water heaters and refrigerators cycle, so the burner runs only part of the time. Using switched-on hours would overstate your use. Compare the estimate with your gauge or scale over the first days and adjust.
Are the BTU constants exact?
No. About 91,500 BTU per US gallon and about 21,600 BTU per pound are approximations of the fuel’s energy content, and the real figure varies slightly with the gas mix and temperature.
What swap level should I choose?
That is your decision. Choose a level that leaves time to reach a refill or swap even if cold weather or an appliance problem raises your use, and do not plan to run the tank empty.
Does this send my numbers anywhere?
No. The calculation runs in your browser and nothing is stored or sent.
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