When I go for a run, I use my Garmin as this allows me to follow pre-set programs.
After said run, it gives me the calories I've just burned, along with the distance / time / speed. I plug the same information into MFP which gives me a drasticly different calorie count. It has been as much as 80-100 calories different, which given I'm only running 2 miles is a bit of a difference. I've checked and MFP and Garmin both think my weight and height are the same so, simply, who to trust?
I know, for reference, you'll want my height and weight but if I do a very different run / lose a few more pounds, the calorie count will be different anyway so is there some basic formula I can use instead of you all telling me what I burned for this specific run?