Method: gas requirements are calculated based on the volume of water to boil (people × boils × days), weighted by stove efficiency, ambient temperature, wind, and altitude, plus a 10% safety margin. For each brand, the recommended canister combination covers your needs using the fewest canisters possible — except on trips of 3 days or more, where the largest canister size is avoided in favour of smaller ones where reasonable (maximum 5 canisters), saving pack space and allowing you to gradually shed empty canisters.

What is the difference between gas canisters? MSR, Jetboil, and Optimus all use standard threaded valves (EN417 standard): canisters from one brand will fit stoves from another. Campingaz is the exception: its Easy-Clic system (clip-on) is not compatible with EN417 screw-on stoves, and vice versa — always check your stove system before choosing a canister. Gas blends also vary: standard canisters (IsoPro, JetPower, Energy, Campingaz CV Plus) feature a butane/propane mix designed for mild conditions, whereas "4-Season" versions (Optimus) contain more propane for improved vapourisation in extreme cold.

Sources and limitations: benchmarks based on REI Co-op and MSR (Cascade Designs) guidelines for trek planning. This is an estimate, not a guarantee: actual efficiency depends on your gear, technique, and factors not modelled here (snow melting, canister wear, etc.). In extreme cold or challenging terrain, always carry a spare canister.