How Long Does a Propane Tank Last?
A full 20 lb propane tank (the standard grill size) contains roughly 432,000 BTUs of energy. At a typical grill burner output of 15,000 BTU/hr, that tank will run for about 20–22 hours at the high setting. For a 1 lb camping cylinder (21,600 BTUs), expect 1–1.5 hours on the same burner. Your actual runtime depends on the appliance’s BTU rating, temperature, altitude, and how full the tank really is.
The quick formula: Tank capacity (lbs) × 21,600 ÷ Appliance BTU/hr = Hours of runtime.
What this means for your next cook or trip: If you’re planning a full weekend of grilling (say, 6 hours total burner time at medium heat), a single 20 lb tank will more than cover it, but a 1 lb cylinder will run out before your first meal. For portable stoves or grills, match tank size to the total cooking hours you actually need—plus a 20% buffer for cold weather or higher flames. Buying a tank that’s too small means a cold meal; buying one that’s too large means you’re carrying unnecessary weight.
Factors That Really Change Your Runtime
Appliance BTU Rating
The single biggest variable. A portable stove may draw 10,000 BTU/hr per burner, while a gas grill can pull 30,000 BTU/hr total. Always check the appliance’s label or manual—don’t guess. Verification step: Locate the BTU rating stamped on the appliance near the gas connection or on a metal plate. If it’s worn off, look up the model number online. Using a higher BTU setting than the rating can starve the burner and produce yellow flames, wasting fuel.
Temperature and Altitude
Propane vapor pressure drops in cold weather. Below 20°F, you might get 30–50% less usable gas because the liquid won’t vaporize fast enough. At high altitudes (above 5,000 feet), the lower air density also reduces efficiency, effectively shortening runtime by 10–20%. Mismatch to watch for: If you’re cooking in sub-freezing weather with a 1 lb cylinder, vaporization can become so weak that the burner won’t stay lit, even if the cylinder is still heavy. In that case, switching to a larger tank (5 lb or 20 lb) gives you more surface area for vaporization and a warmer gas supply.
Tank Condition and Fill Level
The OPD valve stops filling at 80% capacity for safety, so a 20 lb tank actually holds about 16 lbs of propane. Use the actual fill weight (not the cylinder weight) in your calculation. A rusty or damaged valve can also leak gas slowly—more than a minor safety risk, it cuts your runtime. Trade-off: Lifting a tank to judge its remaining fuel is unreliable. A 20 lb tank that feels “half as heavy” might actually be 60% full because the steel shell weighs the same. Always use a scale or gauge for an accurate read.
Quick Runtime Estimates for Common Tank Sizes
| Tank Size | Total BTU Capacity | Hours at 10,000 BTU/hr | Hours at 15,000 BTU/hr | Hours at 20,000 BTU/hr |
|---|---|---|---|---|
| 1 lb | 21,600 | ~2.25 | ~1.5 | ~1 |
| 5 lb | 108,000 | ~10.8 | ~7.2 | ~5.4 |
| 10 lb | 216,000 | ~21.6 | ~14.4 | ~10.8 |
| 20 lb | 432,000 | ~43 | ~28.8 | ~21.6 |
| 30 lb | 648,000 | ~64.8 | ~43.2 | ~32.4 |
These are rough estimates at full burner output. Cooking at a lower flame extends runtime.
How to Calculate Your Own Propane Runtime
- Find your appliance’s BTU/hr rating. Usually stamped near the gas connection or listed in the manual. If you have a dual-burner stove, add both burner ratings together if you plan to use both at once.
- Weigh your tank (or read its fill sticker). A 20 lb tank filled to 80% holds about 16 lbs of propane. For 1 lb cylinders, the weight is the name—1 lb of propane. Verification step: Place the tank on a bathroom scale. Record the weight, then subtract the tare weight (TW) stamped on the collar (e.g., “TW 18.5”). The difference is the actual propane weight.
- Multiply tank propane weight by 21,600 (BTUs per pound). Example: 16 lbs × 21,600 = 345,600 BTUs for a filled 20 lb tank.
- Divide total BTUs by your appliance’s BTU/hr rating. 345,600 ÷ 15,000 = ~23 hours.
Example: You’re using a single-burner stove rated at 10,000 BTU/hr with a 5 lb tank (4 lbs of propane after 80% fill). Total BTUs = 4 × 21,600 = 86,400. Runtime = 86,400 ÷ 10,000 = ~8.6 hours.
Decision Aid: Is Your Propane Setup Cutting Your Runtime Short?
Run through these checks before your next trip or cookout. Each item can reveal up to 30% hidden runtime loss.
- [ ] Appliance BTU rating confirmed? If you guessed the number, check the manual. A 20% higher rating than you think means 20% less runtime.
- [ ] Tank truly full? Use a tank scale or integrated gauge (like the Flame King 5LB Aluminum Propane Tank with Gauge & OPD Valve). A half-full tank gives half the runtime.
- [ ] Ambient temperature above 40°F? Below that, vaporization slows. If you’re cooking in cold weather, expect 15–30% less usable gas.
- [ ] No gas odor or hissing? Smell test and soapy water on connections. A small leak wastes gas and is dangerous.
- [ ] Regulator not frosting? Frost on the regulator indicates liquid propane is getting through, which can starve the burner and reduce output. Replace the regulator if you see this.
Pass all five? Your runtime should match the table above. Fail one? Address it before relying on your calculation.
Expert Tips to Get the Most from Your Propane Tank
Tip 1: Use a tank gauge instead of guessing weight.
- Actionable step: Install an inline gauge (like the one on the Flame King tank) or buy a portable tank scale. Check the reading before every cook.
- Common mistake: Lifting the tank to “feel” how heavy it is. That method is wildly inaccurate—you’ll often leave a meal half-cooked because you overestimated your fuel.
Tip 2: Warm up the tank in cold weather—safely.
- Actionable step: If temps drop below freezing, submerge the tank in a bucket of warm (not hot) tap water for 15–20 minutes before connecting. Never use a flame, radiator, or electric heater.
- Common mistake: Placing the tank next to a propane heater, grill burner, or any direct heat source to warm it up. This can overpressurize the tank and blow the relief valve, or worse.
Tip 3: Match tank size to your actual cook time, not the weekend’s optimism.
- Actionable step: Calculate the total BTU you need for each meal (appliance BTU/hr × hours of cooking). Then add 20% for safety. Choose a tank that covers that number, no bigger.
- Common mistake: Bringing a 1 lb cylinder for a full weekend of high-heat grilling. You’ll run out before the first steak is done. A 5 lb tank gives you a realistic buffer for two meals.
FAQs (Quick Answers to Common Follow-Ups)
Does a propane tank expire?
Yes. DOT tanks are generally certified for 12 years from manufacture. After that, they must be recertified or replaced. An expired tank may leak or fail structurally.
How can I tell if a tank is empty without a gauge?
Weigh it. The empty (tare) weight is stamped on the tank collar (e.g., “TW 18.5”). Subtract that from the current weight. If the difference is less than 0.5 lb, the tank is effectively empty.
Can I run a propane heater and a stove from the same tank?
Yes, but only if the combined BTU draw is within the regulator’s output (typically 100,000 BTU/hr for a standard grill regulator). Running two high-BTU appliances will drain the tank much faster—use the calculator above with the combined rating.
No matter how careful you are, always keep a close eye on your fuel level. A few minutes of upfront calculation can save you a cold meal or a cut-short barbecue.
Camping Bob has spent over 20 years camping across the US — from BLM dispersed sites in the Southwest to KOA campgrounds in the Pacific Northwest. He writes practical, no-nonsense guides to help fellow campers get outdoors with confidence.