Last updated: November 1, 2026
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The short answer: Weigh the canister on a kitchen scale and subtract the empty weight stamped on its base — roughly 95 g for a small can, 130 g for a medium, 195 g for a large. What remains is fuel, in grams. At about 14 grams per liter boiled on a typical upright stove, 70 grams of remaining fuel is about 5 liters of boils: five freeze-dried dinners’ worth, or about two and a half solo days. Shaking the can tells you almost nothing; the scale tells you everything.
Why the shake test lies
Everyone’s first method is to shake the canister and judge the slosh. It fails for a physical reason: what you hear is liquid fuel moving, and a canister that is three-quarters empty and one that is a quarter empty both slosh, at volumes your ear cannot reliably separate — especially through gloves, in wind, at a trailhead. Worse, the shake gives no number, and fuel planning is arithmetic. The question is never “is there some fuel?” — there almost always is. The question is “how many boils?”, and only grams answer grams questions.
The float test sometimes suggested online — part-used canisters float at different angles in water — is better than shaking and still worse than weighing: it is approximate, it needs a bucket of water deep enough to float a canister upright, and it rusts the can’s base over time. A kitchen scale costs little, weighs the rest of your kit too, and reads to the gram. It is the method.
The weighing method, step by step
Weigh the canister as it stands. Find the empty (tare) weight: on most canisters it is stamped or printed on the base or the label as the weight of the empty container — if yours is not marked, use the class figures in the table below, which are close across the major brands because the steel cans themselves are standardised. Subtract. That difference is your fuel.
Prefer not to do the subtraction standing in the garage? Our Canister Fuel-Remaining Calculator takes the scale weight and the canister size and returns the grams left, the liters of boils, and the days — the arithmetic on this page, done for you.
| Canister size | Fuel when full | Empty can weighs | Full can weighs |
|---|---|---|---|
| Small | 100 g | ~95 g | ~195 g |
| Medium | 230 g | ~125–130 g | ~355–360 g |
| Large | 450 g | ~195 g | ~645 g |
Worked example, using the exact shape of the Backpacking Light ask that prompted this page: the fuller canister weighs 12.25 oz, which is about 347 g. If it is a medium can, subtract about 130 g of steel and the fuel inside is roughly 217 g — nearly full, whatever the shake suggested. That asker’s trip needed three 2-cup breakfasts and three 1.5-cup dinners: about 10.5 cups, or 2.6 liters of boils, at roughly 14 grams per liter — call it 37 grams of fuel, plus simmering and priming losses. Against 217 g in the can, the answer is not close: yes, with most of the canister still in hand for the next trip.
Turn grams into boils and days
| Fuel remaining | Liters boiled (upright stove) | Liters boiled (Jetboil Flash class) |
|---|---|---|
| 25 g | ~1.8 L | ~2.5 L |
| 50 g | ~3.5 L | ~5 L |
| 100 g | ~7 L | ~10 L |
| 200 g | ~14 L | ~20 L |
The upright column uses the 14 grams per liter baseline from our camp stoves compared dataset — the MSR PocketRocket 2’s own published rating works out to about 14.2 grams per liter. The right column uses the Jetboil Flash’s roughly 10 grams per liter. In wind and cold, halve the liters: cold canisters lose pressure and every boil stretches, which is the whole subject of why does my canister stove die in cold weather? For days rather than liters, a solo freeze-dried eater boils about 2 liters a day — the full budget is in how much stove fuel do I need per day?
One habit makes all of this effortless next season: when a canister comes home part-used, weigh it, and write the remaining grams on the cap or the can with a marker, with the date. Future you, packing at 10 p.m., gets a number instead of a mystery — and a shelf of mystery cans is how people end up carrying two part-used canisters “to be safe,” which weighs more than one full one.
Questions readers ask next
Can I top up or refill a part-used canister from a full one?
Adapters exist, and we do not recommend the practice. Refilling transfers fuel between pressurised containers never designed to be consumer-refilled, invites overfilling — a can filled without headspace on a cold morning becomes a hazard on a warm afternoon — and voids whatever standing the canister had. Part-used cans are a planning problem; the scale and the marker solve it without turning it into a safety problem.
How do I know when a canister is truly empty and ready to recycle?
When the stove will no longer light from it and the scale says the can is at its stamped empty weight, the fuel is effectively gone — a gram or two of vapour may remain. To recycle, the can must be fully vented and punctured with the tool sold for the purpose, following your local recycling rules; a can that still hisses is not empty and does not go in the bin.
Does a cold canister weigh the same?
Yes — cold changes the fuel’s pressure, not its mass, which is precisely why weighing beats judging by how the stove performs. A can that flames weakly on a frosty morning may hold 150 g of fuel that will burn perfectly well once the can is warmed in a jacket or a bowl of water. Weigh first; warm second; condemn last.
More questions like this: this page is one answer from What People Are Asking About Stoves and Fuel — the full set of stove and fuel questions, with the short answers, lives there.
Keep reading
This answer belongs to What People Are Asking About Stoves and Fuel, our hub for the stove and fuel questions readers actually type. It pairs with how much stove fuel do I need per day? — together they are the whole fuel plan — and the stoves behind its grams-per-liter figures are compared in camp stoves compared.
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