Checked against its sources on October 21, 2026
Divide the energy in the tank by what your burner uses an hour. An exchanged 20-lb tank holds about 323,000 BTU, so a 10,000 BTU burner on high runs about 32 hours. A tank refilled at a station holds about 431,000 BTU, about 43 hours on the same burner.
A “20-lb” tank does not always hold 20 pounds. Tanks you swap at a store hold 15: AmeriGas says its exchange tanks “contain a net weight of 15lbs of propane”. A tank you hand over to be filled from a hose at a station is filled to about 20 pounds. Propane holds 21,548 BTU per pound (Propane Education & Research Council), so:
Find the BTU rating on your stove or heater; it is printed on the label or in the manual, usually for the high setting. Then read across:
| Burner uses | For example | Exchanged tank | Refilled tank |
|---|---|---|---|
| 4,000 BTU an hour | Small heater on low | about 81 hours | about 108 hours |
| 9,000 BTU an hour | Small heater on medium | about 36 hours | about 48 hours |
| 10,000 BTU an hour | One camp-stove burner | about 32 hours | about 43 hours |
| 18,000 BTU an hour | Small heater on high | about 18 hours | about 24 hours |
| 20,000 BTU an hour | Two camp-stove burners | about 16 hours | about 22 hours |
The heater rows use the settings of a Mr. Heater Big Buddy, which runs 4,000, 9,000 or 18,000 BTU an hour. Labels usually give the high setting; on a lower setting the same tank lasts longer.
MyPlann plans 7,000 BTU of cooking a day per person, which is deliberately generous: in an outage you boil water and cook from scratch on a camp stove. At that rate a family of four gets about 11 days from an exchanged tank and about 15 from a refilled one.
Use a camp stove or grill outdoors unless its maker says it is safe indoors. Never heat your home with a gas range or oven, never burn charcoal indoors, keep a generator at least 20 feet from windows and doors, and put a battery-powered carbon monoxide alarm near where people sleep. Those are the CDC’s rules.
MyPlann counts every 20-lb tank at 15 pounds to be safe, because most people exchange their tanks. If you refill yours, you can set your tanks that way in Supplies. Every rate it uses, and its source, is on How MyPlann Counts.
MyPlann counts days for water, food, cooking fuel, heat and medicine from what is actually in your house, and tells you which runs out first. Get your number; it is free during early access.