YEAH SO if you burn off 3500 + whatever you ate that day for example 1200 calories then theoretically you lose a pound.
However that is a huge amount of calories to burn in a day, and even though you burn a certain of calories a day just by living, it would take a lot of work to burn that much excercising.
Not much help I kno sorry and no easy solution, but U did ask for a formula so...
1lb. weight loss = burning 3500 calories + (amount of calories you eat in a day)