For me, it underestimates the ones burned by exercise, gets the BMR right (well, as right as it can be without including body fat % - close enough), but really overestimates how many calories I burn just sitting on my tush on a computer all day. When I was not in ketosis, I got a pretty clear picture of what my maintenance calories are, and they are lower than what FitDay has me at, even with the exercise underestimation.