A full 20 lb propane tank holds about 4.7 gallons of propane, or about 430,000 BTU. On a typical 3-burner grill rated 30,000–40,000 BTU, that's roughly 10–14 hours with every burner on high and much longer at medium; our Weber Spirit E-325 ran 18–20 hours on one tank at medium heat. A 1 lb canister lasts about 1–2 hours on a portable grill on high.
To know what's left, weigh the tank and subtract the tare weight stamped on the collar. Trust the scale, not the gauge.
What do you need to know about your tank?
Pick your question and jump to the answer.
| You want to know | Short answer | Go to |
|---|---|---|
| Hours from a 20 lb tank | 10–14 on high, far more at medium | Burn times |
| Hours for your exact grill | 430,000 ÷ your grill's BTU | The math |
| How long a 1 lb canister lasts | About 1–2 hours on high | Canisters |
| How much is left right now | Weigh it, subtract the tare | Check your level |
| Why it ran out so fast | Usually heat, lid or a short fill | Fast-draining tank |
| Whether to refill or swap | Refill is usually cheaper | Refill vs exchange |
How long does a 20 lb tank last on your grill?
Bigger grills burn faster, but most cooks never run every burner on high.
These are rough estimates for a full 20 lb fill, assuming about 10,000 BTU per burner on high, about half that at medium and a quarter at low. Valve output at medium and low varies by grill, so treat the right-hand columns as ballpark figures.
| Burners lit | Total BTU on high | All on high | All on medium | All on low |
|---|---|---|---|---|
| 2 | 20,000 | About 21 hours | About 43 hours | About 86 hours |
| 3 | 30,000 | About 14 hours | About 29 hours | About 57 hours |
| 4 | 40,000 | About 11 hours | About 21 hours | About 43 hours |
| 6 | 60,000 | About 7 hours | About 14 hours | About 29 hours |
At the medium-heat burn time we measured on the Weber Spirit E-325, a household that grills a few nights a week goes through a tank every few weeks in summer.
Searing and long preheats pull that number down. Run the Sear Zone or every burner on high and you move toward the table's full-output figure.
How do you work out burn time for your grill?
Divide the tank's BTU by your grill's BTU to get hours on high.
Propane holds about 21,500 BTU per pound, or about 91,500 BTU per gallon, which is where the 430,000 BTU figure for a full tank comes from.
- Find your grill's total BTU on the label, manual or spec sheet.
- Add any sear, side or rotisserie burner you actually use; each has its own rating.
- Divide 430,000 by that total to get hours with everything on high.
Take the Weber Genesis E-325: its three main burners total 39,000 BTU, so a tank runs about 11 hours flat out. Light its 13,000 BTU sear burner too and you're at a little over 8 hours.
A grill's BTU rating is its maximum hourly input with every main burner on high. At medium the valves pass much less gas, which is why ordinary weeknight cooks stretch a tank so far.
For a per-cook estimate, a 30,000 BTU grill on high burns about 1.4 lb an hour. A 15-minute preheat on high uses about a third of a pound before any food goes on.
How long does a 1 lb propane canister last?
Expect about 1 to 2 hours on high, depending on the burner.
A 1 lb canister holds about 21,500 BTU. On the 11,000 BTU burner of the Megamaster Tabletop 1-Burner we tested, that's about 2 hours on high. A two-burner portable at 12,000 BTU total, like the Napoleon TravelQ PRO285X, gets under 2 hours.
One cylinder covers a lunch cook; pack a second for anything longer.
Per pound, canisters are the most expensive way to buy propane. If you grill weekly on a portable, an adapter hose to a 20 lb tank pays for itself. Some portables, like the Cuisinart Portable Propane Grill, are built to run on a 20 lb tank from the start, which gives its 20,000 BTU of burners roughly 21 hours on high.
Most 1 lb cylinders are disposable and not designed to be refilled. Take empties to a propane retailer or household hazardous waste site.
Step-by-Step: How to Check Your Propane Level
Weighing the tank is the only reading you can trust.
Step 1 of 5Find the tare weight
Target: the number after 'TW' on the tank collar
The tare weight is what the tank weighs empty, usually about 17–18 lb for a standard 20 lb tank. Write it on the tank with a marker so you don't have to hunt for it next time.
Step 2 of 5Weigh the tank
Done when: you have the total weight in pounds
Close the valve, disconnect the tank and stand it on a bathroom or luggage scale. A tank with a true 20 lb fill weighs about 37–38 lb.
Step 3 of 5Subtract to get the fuel left
Target: pounds of propane remaining
Fuel left = total weight minus tare weight. Multiply by 21,500 and divide by your grill's BTU for hours on high. Under 5 lb left is a good point to swap or refill.
Step 4 of 5Or use the warm-water method
Time: about 1 minute
Pour a cup of warm tap water down the side of the tank, then run your hand down it. The tank feels cool where the liquid propane starts, because the liquid absorbs the heat.
The cool band marks the liquid line; it's a rough read, not a substitute for weighing the tank.
Watch out: use warm tap water, never boiling water or a flame, to warm or test a tank.
Step 5 of 5Keep a spare
Done when: a full tank is waiting before the current one runs low
A spare means you never run out mid-cook. Swap the empty for a full one on your next errand, not the next time you need it.
Why is your propane tank running out so fast?
A fast-draining tank usually comes down to heat, habits or a short fill.
You cook hot with the lid open
Sign
a tank empties in far fewer cooks than the math predicts.
Fix
- Preheat with the lid closed for 10–15 minutes, no longer.
- Turn off burners you aren't cooking over, and use a sear burner only while searing.
Expect
noticeably more cooks per tank. Our guide to how long to preheat a grill gives preheat times by fuel.
The tank wasn't full to begin with
Sign
a "new" exchange tank weighs well under 37 lb.
Fix
- Weigh exchange tanks when you bring them home (Step 2).
- Refill your own tank at a station that fills by weight.
Expect
a full 20 lb of propane instead of the 15 lb many exchange tanks carry.
There's a leak
Sign
a rotten-egg smell near the tank or hose, or a tank that loses weight between cooks.
Fix
- Close the valve and brush soapy water on the connection and hose.
- Tighten or replace anything that bubbles before you light the grill.
Expect
no bubbles and no weight loss while the grill sits unused.
The flame is weak on a full tank
Sign
low, lazy flames even though the scale says the tank is full.
Fix
- Turn every burner and the tank valve off, disconnect the regulator and wait a minute.
- Reconnect, open the tank valve slowly, then light one burner at a time.
Expect
full flames again. If the grill still runs cold, work through grill not heating up properly.
Does propane work in cold weather?
It works below freezing, but a cold, low tank makes less gas.
Propane boils at about -44°F, so it still turns to vapor in winter. The colder the liquid, though, the less vapor it makes and the lower the pressure, so a nearly empty tank may not keep up with a big grill on high.
- Start winter cooks with a tank at least a third full.
- Run fewer burners on high and keep the lid closed.
- If the tank frosts over, it's vaporizing faster than it can absorb heat; turn burners down or switch tanks.
Cold also means longer preheats, so budget extra fuel from November to March. Our winterizing checklist covers what to do with the tank if you stop grilling for the season.
Should you refill or exchange a propane tank?
Refill for the most fuel per dollar; exchange for speed or an expired tank.
| Factor | Refill | Exchange |
|---|---|---|
| Fill level | Filled to the full 20 lb safe limit | Often filled to 15 lb, not 20 |
| Convenience | Need a refill station | Cages at many stores |
| Tank | You keep yours | You get a different tank |
A "20 lb" tank is never filled to the brim. Tanks up to 40 lb must have an overfill prevention device (OPD) valve, which stops filling at about 80% of capacity to leave room for the liquid to expand as it warms.
Tanks also carry a requalification date. A DOT cylinder is due 12 years after the manufacture date stamped on the collar, then on a shorter cycle after that. A refill station won't fill one that's out of date, but an exchange solves that.
How do you store and handle propane safely?
Keep the tank upright, outdoors and closed whenever you aren't cooking.
- Store tanks upright and outdoors, never inside a house, basement or closed garage.
- Close the tank valve every time you finish grilling.
- Leak-test with soapy water after every tank change.
- Carry tanks upright and secured, with the valve closed and a window open, and never leave one in a hot car.
Shade the tank on hot days; heat raises the pressure inside it.
Propane itself doesn't go bad; the tank, valve and hose are what wear out. If the burners won't catch after a tank swap, our gas grill ignition troubleshooting steps start with the likeliest cause.
You should see: steady blue flames with yellow tips at most. Mostly yellow, sooty flames mean a burner or venturi problem, not a tank problem.
Which grills go easiest on propane?
Match the grill's BTU to what you cook instead of buying the biggest.
A bigger grill isn't the answer to running out; matching burners to your cooking is. A 31,000 BTU three-burner with a Sear Zone lets you sear a steak over one section instead of running the whole grill on high.
- Small household: a 3-burner grill uses less fuel than a 5-burner you never fill; compare picks in our best gas grills under $500.
- Big cookouts: buy the big grill, but keep a second full tank on hand.
- Tailgates and camping: a low-BTU portable on a 20 lb tank runs for days; see our best portable grills.
- You smoke on gas: budget about one burner on low for the whole cook, and start with a full tank.
- You keep running out mid-cook: weigh the tank before every long cook.
Efficient 3-burnerWeber Spirit E-325★ 4.5/5
31,000 BTU, and a 20 lb tank lasted roughly 18–20 hours at medium in our testing.
Big propane grillWeber Genesis E-325★ 4.6/5
39,000 BTU of main burners plus a 13,000 BTU sear burner; weigh the tank before big cooks.
Fuel-sipping portableNapoleon TravelQ PRO285X★ 4.5/5
12,000 BTU total, so a 20 lb tank runs it for roughly 36 hours on high.
Still not fixed? A full tank but a weak flame usually means a tripped regulator; reset it with our guide to a grill not heating up properly. Time for a new grill? Our gas grill reviews cover every model we've tested.
Frequently Asked Questions
01How long does a 20 lb propane tank last on a grill?
About 10–14 hours on high on a typical 3-burner grill, and far longer at medium. A full tank holds about 430,000 BTU, so divide that by your grill's total BTU for hours with every burner on high. Smaller grills get more hours, bigger ones fewer, and sear or side burners shorten the time further.
02How many cookouts do you get from a 20 lb tank?
It depends on the cook, so count hours rather than cookouts. Quick burger nights stretch a tank much further than long indirect sessions on one burner. A 30,000 BTU grill on high burns about 1.4 lb an hour, and a 15-minute preheat uses about a third of a pound. Weigh the tank before a long cook so you know where you stand.
03How long does a 1 lb propane tank last?
About 1–2 hours on high on a portable grill, depending on the burner. A 1 lb canister holds about 21,500 BTU, so a single 11,000 BTU burner gets about 2 hours. If you grill weekly on a portable, an adapter hose to a 20 lb tank is far cheaper per cook than canisters.
04How much does a full 20 lb propane tank weigh?
About 37–38 lb with a true 20 lb fill. The empty tare weight stamped after "TW" on the collar is usually about 17–18 lb. An exchange tank filled to 15 lb weighs about 5 lb less. Subtract the tare from the scale reading to see how many pounds of propane are left.
05Are tank pressure gauges accurate?
No. Pressure follows temperature, not the amount of liquid, so a gauge reads near full until the tank is almost empty. Weigh the tank instead, or use the warm-water method for a rough read: the tank feels cool where the liquid starts. Plan to swap or refill once under 5 lb of propane is left.
06How long are propane tanks good for?
The propane itself doesn't go bad; the tank ages instead. In the US, a 20 lb cylinder must be requalified 12 years after the manufacture date stamped on its collar, then on a shorter cycle. Refill stations won't fill an out-of-date tank, but an exchange service hands you a current one.
07Why does my propane tank say full but the flame is weak?
A tripped regulator is the usual cause, not the tank. Turn every burner and the tank valve off, disconnect the regulator and wait a minute. Reconnect, open the tank valve slowly, then light one burner at a time. If flames stay low and lazy, check the burners and venturi tubes for blockages.
08Can I use a 20 lb tank on a portable grill?
Yes, with an adapter hose made for your grill's regulator. It's far cheaper per cook than 1 lb canisters, and a low-BTU portable on a 20 lb tank runs for days. Some portables are built to run on a 20 lb tank from the start. Leak-test the hose with soapy water after you connect it.
The Takeaway
Divide 430,000 by your grill's BTU and you know your worst-case burn time. Weigh the tank to see what's left, keep a spare, and give yourself extra margin in winter.
If you're shopping for a new grill, pick the burner count you'll actually use.
Written by
Tom Bricker
Consumer Research Analyst & Lead Tester
Tom Bricker has 10+ years of grilling on every fuel type and a consumer-research background. He leads SmokyHQ’s gas, portable, electric and flat-top testing, so if you’re weighing price against how long a grill will last, his reviews show which ones are worth the money.
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