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Free tool · RV propane

How long will your propane tank last?

Pick your tank size, tick the propane appliances you run, and this tool returns how long the tank lasts: days of runtime, the furnace-only figure, and your daily burn, using propane's real energy content. A planning estimate, with the cold-weather and carbon-monoxide cautions most calculators leave out.

Read first (safety): this is a free planning estimate, not a measurement of your tank. Real burn depends on your appliances, the weather, and the wind. More important than the math: never use a stove, oven, or an unvented portable heater to heat an enclosed RV or tent. Burning propane indoors makes carbon monoxide and uses up oxygen, and it kills people every season. Run a working CO detector and a propane (LP) detector, ventilate when you cook, and treat any gas smell as a stop-everything event.

Your tank

Your appliances

Tick what you run and set BTU/hr and burn hours per day. For the furnace and water heater, hours means effective burn time (they cycle); for the stove and grill it is actual burner-on time. When unsure on the furnace, estimate high so you plan to refill early rather than run out in the cold.

Use Appliance BTU/hr Hrs/day
cycles on and off, so enter EFFECTIVE burn time, not clock hours: roughly 3 to 5 hrs on mild nights, 6 to 9 in cold, 10+ in a deep freeze. The winter tank-drainer; when unsure, estimate high
cycles; about an hour of actual burn a day in normal use
actual burner-on time
runs continuously at a low rate; not a 12V compressor fridge
ventilation and a CO detector required; never as primary indoor heat
actual cook time
actual burn time, both burners

A planning estimate using propane's standard energy content. Your real burn varies with weather and use; weigh the tank for the true level.

How the propane math works

The calculator above is just this method, applied to your tank and appliances. You can run it by hand.

Step 1: Start with the energy in the tank, not the gallons on the sticker

Propane carries about 91,500 BTU per gallon, or roughly 21,500 BTU per pound. A tank rated in pounds is rated by the weight of propane it holds, filled to only 80% to leave room for the liquid to expand, so a 20-pound tank holds about 4.6 usable gallons, near 430,000 BTU, not 20 gallons. The common tank presets in the calculator already account for the 80% fill, and an onboard RV tank rated in gallons is taken at 80% of its stated capacity.

Step 2: Add up what your appliances burn

Each propane appliance has a BTU-per-hour rating, and runtime is the tank's energy divided by the total burn rate. Cooking appliances are on-demand, so you count the actual minutes a burner is lit. The furnace, water heater, and absorption fridge cycle on and off, so what matters is their effective burn time: a 30,000 BTU furnace that runs about a third of a chilly day burns far less than its rating suggests, while a fridge sips a steady 1,500 BTU an hour around the clock. Enter realistic burn hours and the tool totals the daily draw.

Step 3: In winter, the furnace is the hog

On most trips the stove and water heater barely move the needle; the furnace is what empties a tank. As it gets colder the furnace cycles more often, so its effective burn time climbs, and a 20-pound tank that lasts a week in mild fall weather can drain in two or three days when the overnight lows turn hard. If you camp in the cold, size up to a 30 or 40-pound tank or carry a spare, and set the furnace hours high in the calculator to see the cold-weather reality before it strands you.

Step 4: Your tank gauge is probably lying

The cheap pressure and color gauges that screw onto a tank or regulator read vapor pressure, which tracks temperature far more than how much liquid propane is left, so they routinely read near full until the tank is nearly empty. A float-style dial gauge tracks the level better, but only roughly, and it lags while you drive. The reliable method is to weigh the tank and subtract the tare weight stamped on the collar (the TW number), with the remainder being the pounds of propane left, or to use a luggage-style scale. Plan your refills on weight or on a calculator like this one, not on the dial.

Step 5: Cold limits supply, and never heat an enclosed rig with an open flame

Two safety realities. First, in deep cold a small tank cannot vaporize propane fast enough to feed a big furnace, so the flame can starve even with fuel left; a larger tank or keeping it warmer helps. Second, and more important: never use a stove, oven, or an unvented portable heater to heat an enclosed RV or tent. Propane burning indoors produces carbon monoxide and consumes oxygen, and people die from it every season. Run a working carbon monoxide detector and a propane (LP) detector, ventilate whenever you cook, and treat any gas smell as a stop-everything event.

Typical propane appliance BTU reference

Representative BTU-per-hour ratings for common RV and camping propane gear, the figures the tool starts from. Yours vary by model, so check the label. The furnace is almost always the appliance that empties the tank.

Appliance Typical BTU/hr Effective hrs/day
RV propane furnace 30,000 4
RV water heater (propane) 10,000 1
Stove / cooktop burner 7,000 1
Absorption fridge on propane 1,500 24
Portable propane heater (Buddy type) 8,000 3
Outdoor grill 30,000 0.5
2-burner camp stove 20,000 0.5

The propane gear behind the numbers

The appliances this tool sizes for, and the propane-free alternative to the thirstiest one.

Tracking your electric side too? The RV Battery Runtime Calculator does the same job for your 12V battery bank. A worthwhile cheap upgrade for any propane user is a real tank scale or a magnetic level gauge, since the dial gauges that ship on regulators are unreliable.

How we are paid: some links above go to Amazon, and if you buy through them we earn a commission at no extra cost to you. It does not change what we recommend.

Common questions

How long will a 20lb propane tank last on an RV furnace?

Roughly 3 to 7 days in mild cold, and as little as 2 to 3 days in a hard freeze, running the furnace as your main appliance. A 20-pound tank holds about 430,000 BTU. A typical 30,000 BTU RV furnace cycles on and off, burning maybe a third of a chilly day, so it averages around 80,000 to 120,000 BTU a day in mild weather, which works out to several days. As it gets colder the furnace runs more, the effective burn climbs, and the same tank can empty in 2 to 3 days. The calculator above lets you set the furnace hours to match your weather.

How do I calculate how long my propane tank will last?

Take the tank's energy in BTU (about 91,500 BTU per gallon, or 430,000 BTU for a filled 20-pound tank) and divide it by your total burn rate. Each appliance's burn is its BTU-per-hour rating times the hours it actually burns, and for cycling appliances like the furnace you use effective burn time, not clock hours. Add the appliances together for the daily draw, then divide tank BTU by daily BTU for days of runtime. The tool does this from the tank and appliances you select.

How many BTU are in a propane tank?

Propane holds about 91,500 BTU per gallon (roughly 21,500 BTU per pound). Because tanks are rated by the weight of propane and filled to 80% for safety, a 20-pound tank holds about 4.6 usable gallons, near 430,000 BTU; a 30-pound tank about 640,000 BTU; a 40-pound tank about 860,000 BTU; and a 100-pound tank about 2,160,000 BTU. An onboard RV tank rated in gallons is figured at 80% of its stated capacity times 91,500.

How long will a propane tank last on a grill?

A standard 20-pound grill tank lasts roughly 18 to 20 hours of cooking on a medium-sized grill, dropping toward 10 hours on a large grill running hot. The math: about 430,000 BTU in the tank divided by the grill's total BTU-per-hour. A 30,000 BTU grill on high burns through it in about 14 hours of actual cook time; turned down, it stretches much further. Most people get many weekends of grilling from one tank, since the actual burner-on time per cookout is short, though it depends on how long and hot each session runs.

Why does my propane tank gauge read full when it's almost empty?

Because the cheap screw-on pressure and color gauges read vapor pressure, not liquid level, and vapor pressure depends mostly on temperature (a float-style dial gauge reads the level, but only roughly). On a warm day a nearly empty tank can still show a healthy reading, then drop to empty quickly. The accurate way to check is to weigh the tank and subtract the tare weight stamped on the handle or collar (marked TW), which leaves the pounds of propane remaining, or use a luggage scale. Refill on weight, not on the dial.

Is it safe to heat an RV or tent with a propane stove or heater?

No, not with an open flame in an enclosed space. Never use a stove or oven to heat an RV, and never run an unvented portable propane heater in a closed rig or tent as your main heat. Burning propane indoors produces carbon monoxide and uses up oxygen, and it kills people every camping season. Use a properly installed, vented RV furnace for heat, run a working carbon monoxide detector and a propane (LP) leak detector, ventilate whenever you cook, and if you ever smell gas, shut off the tank and air the space out before doing anything else.

Disclaimer

This calculator is provided for general informational and educational purposes only and gives a planning estimate based on propane's standard energy content as of 2026. It is not a measurement of your tank and not a substitute for weighing it or for a qualified RV or propane technician. Real consumption varies with appliance condition, thermostat settings, weather, wind, altitude, and the cold-weather vaporization limit. Propane is a flammable gas that produces carbon monoxide when burned: never use a stove, oven, or an unvented heater to heat an enclosed space, always run working carbon monoxide and propane leak detectors, have your propane system and appliances serviced by a qualified technician, and follow all manufacturer and code requirements. We make no warranty as to accuracy, and accept no liability for any loss, injury, fire, or carbon-monoxide harm arising from reliance on this information. When in doubt, consult a qualified professional. Last reviewed June 2026.

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