It varies a lot between hikers. Some people are 4 cup a day regular hot drinkers. Unbelievably, there are also hikers who don’t drink tea or coffee at all! Some people prefer to cook on their stoves and some rely solely on boiling water to rehydrate their freeze dried meals. Some hikers boil water to clean their utensils after eating and some just wipe their pot out. The type of stove you use is important too. There is a great variance in how much fuel you will use based on your own personal needs.
There are also lot of uncontrollable variables too, these can change the amount of fuel you use from trip to trip and day to day; ambient temperature, starting temperature of the water, wind, elevation, fuel quality.
A note on stove type; stove systems such as the Jetboil or MSR Windburner which have integrated wind protection and heat exchange features are far more efficient in their gas usage than open stoves such as the MSR Pocket Rocket, Optimus Crux or 360degrees Furno. You really can halve the amount of fuel required when using a Jetboil or MSR Windburner over an open stove.
Using Jetboils’ own calculations documented as a handy pictorial on the side of their canisters it tells you how many boils (of 500ml of water) you’ll get out of each canister size, they suggest a 100gm canister will give you 24 boils. It is simplifying things a bit, but that’s about 48 cups (250ml) of boiled water.
Here’s the important bit! If you can calculate how many cups of water you need to boil each day you can work out how far each 100g of gas will go. Using Jetboils’ calculations above you will get about 48 cups of boiled water out of a 100g Jetboil canister using a Jetboil stove. If you double usage for an open stove, that’s 24 cups of water boiled out of 100g. Remember those variables though – wind, temperature etc etc, they’re potentially going to increase usage and so is the size of your cup! So build a small buffer into your calculations.
For me and my walking buddy, we start the day with a cup of tea, rarely miss a mid morning coffee maybe even an end of day cup of tea, followed by some hot water to rehydrate dinner, and a cuppa after dinner – I know…. So, that 100g canister will last about 4 days using the Jetboil, and 2 and a bit days with the Optimus Crux.
What if I’m using liquid fuel?
Liquid and spirit stoves tend to use a little more fuel than canister stoves but have the advantage of offering consistent heat at both cold and warm temperatures, so it removes the weather variable that affects canister stoves. Liquid fuel also has the advantage of being able to be seen and measured so you can accurately gauge how much fuel you’re using or have left. This makes it much easier for you to calculate how much fuel you need to take based on how long your fuel takes to boil a litre of water and how many boils you need in your day.