I found this interesting blog that will calculate your calories used while hiking. I don’t know how accurate it is, but it at least gives you an idea of calories burned based on a specific trip. It takes your distance, elevation, pack weight and body weight and spits out a number of calories. It seemed pretty reasonable to me but does not take into account any of the other running around you do while on a backpacking trip, nor basal metabolic rate. Be sure to carry more calories then you see from the calculator. I would bring at least another 500 – 1000 calories based on how active you are in camp and how much extra “food” you carry around your waist. It gives you a ballpark to work with when planning for trips at least. Check it out and let me know what you think!