Your TM reading is probably not terribly accurate b/c it is not taking into account your fitness level, probably not your age/weight/height (or maybe some of those but not all), your heart rate unless you wear a strap (do you?) I know my TM came with a strap so I could use it without the watch part, and therefore not know what my calorie expenditure was unless I was on the TM. If, however, you are just going by numbers that the TM generates, without HR and other info, and you really want to track calories burned, invest in a heart rate monitor. They are, as ShyWolf said, quite accurate.