How many calories will you burn for running on a treadmill?

When it comes to burning calories, your heart rate is much more important than what you are doing. If you can reach and sustain the same heart rate forthe same amount of time you will burn pretty much the same amount of calories regardless of activity.

The actual burn rate will depend on how hard you go at it, how fit you are, what you weigh, what your proportion of muscles are etc. I can do about 700-900 cal/hour on a treadmill, but someone smaller and/or less fit might struggle to hit 600. Someone bigger/fitter/younger than me might hit 1100-1300.