Generally, this time of year my camp gear storage area is littered with numerous full, half-full and possibly empty camp stove fuel canisters. I love how efficient and lightweight these (iso)butane/propane stoves are, but it’s quite annoying to try and figure out if one of your used canisters has enough fuel to be packed out for a future trip.
There are various ways to measure the amount of canister fuel. The first is quite simple, but not the most effective. Just shake it and judge the amount of its contents by how much fuel you feel and hear sloshing around in there. This method takes some practice to perfect.
The second method is using a kitchen scale. Weigh an empty canister, then a partially used canister. By subtracting the empty weight from the partially used weight, you will know how much fuel is remaining (grams or ounces).
A third method it to float the canister in a pot of water. A full canister is heavier than an empty one. You can judge the amount of fuel remaining by the position of the water line. A full canister will sink, with only the top section above water (like an iceberg), an empty canister will float and a half-empty canister will bob halfway. Some fuel canisters (like MSR) have a gauge printed on the side. Since the canister has a concave bottom, make sure to place it in the water at an angle first to “burp” the air from the bottom.
The fourth method—my preferred method—is using the JetBoil Jet Gauge. For under $20, you’ll be able to quickly and accurately measure the grams or percentage of fuel left in the canister. You screw the canister onto the hand scale device, set it at either just “grams” or the grams of the size of the canister (100 g, 230 g, 450 g). Place the canister on a flat surface, pick it up while holding the scale, and then read either the number of grams left or the percentage of fuel left in the canister. You can weigh any canister, but the Jet Gauge is calibrated to the weight of a Jet Boil fuel canister, making it more accurate.
Check out my new video below on Ways to Measure Canister Fuel for more details.