This conundrum has left many a multiday tramper pondering whether a morning coffee is wise, given the risk of cold dehy meals for the rest of the trip.

Of course, careful planning ensuring more fuel than you’ll need is the obvious answer to making sure you don’t run out. But there is one little trick to give you a reasonable estimate of what’s left in the canister:

• For this trick you’ll need two canisters of the same make and size – one full, one empty
  

• Place the empty one into a pot of water
  

• Using a permanent marker pen, note where the waterline is and mark this level in the same spot on the full canister

• Place the full canister into the same pot of water
  

• Mark the waterline so you now have two marks – one for full, one for empty
  

• When on the trip, place the canister into water to see roughly how much fuel you have left. It’ll act like a fuel gauge with the waterline falling the more fuel you use