I recommend cooking at least one representative day of food at home and then use the amount of fuel consumed to estimate how much fuel you will need on the trail. For example, if you plan on boiling just 2 cups of water a day then I would recommend boiling 2 cups of water at home using your stove. Then use the amount of fuel you consumed to calculate how long a full tank of fuel would last while hiking. Below is a step by step procedure on how to estimate how long your fuel will last while backpacking.
Step 1: Read the Manual
Follow the stove recommendations for the safe operation of your stove. Each stove comes with a manual.
Step 2: Use a Scale
Weigh the fuel canister and write down the weight before using the stove.
Step 3: Cook
Use the stove for cooking each representative meal for the day. This might be three meals or just one. For a crude estimate you can just boil the amount of water you need for each meal.
Step 4: Weigh Again
Weigh the fuel canister after cooking a representative full day of meals. Record the weight on paper.
Step 5: Calculations
Take the weight of the canister before cooking and subtract the weight of the canister after cooking. The weight difference is the approximate amount of fuel you will use in a day of cooking.
In this demonstration the weight of fuel canister was 262 grams before cooking and 252 grams after cooking. The weight difference was 10 grams which is the approximate fuel that will be used in a day of cooking.
Step 6: Calculations
Look at the fuel weight printed on the side of the canister. Divide the canister fuel weight by the amount of fuel you used to cook a day of food. The result equals the approximate days a full fuel canister will last while hiking.
Here’s an example of how many days a 220 gram fuel canister will last:
Fuel Tip: Have a partial canister and want to know how much fuel is left?
Weigh a full canister of the same brand and size. Then weigh the partially full canister. The difference in the weight between the full canister and the partial canister is equal to the amount of fuel consumed in the partially full canister. Subtract the difference from the marked weight of the full canister. This is the amount of fuel that remains in the partial canister.