reading a running book at the moment by hal higden. in this he says that walking a mile burns approx 100 calories, but if you run that same mile you also burn 100 calories. so, if you run you just burn it quicker
I have a treadmill & have used the treadmills at the gym & they give different readings to each other. but both give me a reading of between 65-75 per mile.
I have therefore decided that I like this "rule" of 100 calories per mile & so prefer to use it as a guide.
just thought I would mention it in case someone is weight watching by calorie intake & this could help with working out extra calories earnt on your run & how much extra you may need to fuel that exercise