The honest answer is "it depends" — on how much gas is in the tank and how thirsty your grill is. Here is the actual math, the real numbers, and a calculator that does it for you.
Calculate my grilling timeEvery "how long will my propane last" question comes down to a fuel tank and a burn rate, exactly like miles per gallon in a car. Propane stores a fixed amount of energy, and your grill burns through it at a rated speed measured in BTU per hour. Put those together and you have hours of grilling.
One pound of propane releases about 21,594 BTU. A full "20 lb" tank holds roughly 20 pounds of propane, which is about 432,000 BTU of energy. Your grill's total output is the sum of all its burner ratings. The formula is simply:
How much propane it holds full: 20, 30, 40, or 100 lb are the common sizes.
How much is actually left right now — best found by weighing the tank.
The combined output of every burner you light, from the rating plate.
These figures assume a full tank with every burner running at full output — a conservative estimate. On medium heat, expect noticeably more time.
| Tank (full) | Energy | 30,000 BTU/hr | 40,000 BTU/hr | 60,000 BTU/hr |
|---|---|---|---|---|
| 20 lb | ~432,000 BTU | ~14.4 hr | ~10.8 hr | ~7.2 hr |
| 30 lb | ~648,000 BTU | ~21.6 hr | ~16.2 hr | ~10.8 hr |
| 40 lb | ~864,000 BTU | ~28.8 hr | ~21.6 hr | ~14.4 hr |
| 100 lb | ~2,160,000 BTU | ~72 hr | ~54 hr | ~36 hr |
To translate hours into cookouts, divide by the length of a typical session. If you grill for about an hour at a time, a full 20 lb tank on a 40,000 BTU/hr grill is roughly ten to eleven cookouts at full blast — and often more in practice.
The calculator gives full-output run time, but a few things change the real number:
About 14 hours on a 30,000 BTU/hr grill, 10–11 hours on 40,000, and 7 hours on 60,000 — at full output from a full tank. On medium it lasts considerably longer.
A full 100 lb tank holds about 2,160,000 BTU — roughly 54 hours on a 40,000 BTU/hr grill, or 36 hours on a 60,000 BTU/hr grill. That is usually a whole season of weekend cookouts.
No. Sealed in the tank, propane keeps its energy indefinitely, so the grilling time it holds does not shrink. Tanks do carry a safety certification date (requalify after 12 years, then every 5), but the fuel itself is fine.
Stop guessing and never get caught half-cooked:
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Enter your tank, fuel level, and grill BTUs — the answer is instant.
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