My Fitbit says my average daily calorie burn is 3560 calories.  I can guarantee that if I ate 3560 calories/day I'd be shaking my flabby arms on YouTube within the month. I do like the Fitbit, and it does help me keep track of my activities (I walk a lot and never considered that exercise, but for calorie expenditure, I'm starting to acknoledge it), but the quality is absolutely awful (I'm on my 3rd Surge after 2 warranty replacements, and counting the days before my Garmin gets here so I can sell this one before it self-destructs too, both of my parents are on their 2nd Charge HR, and several friends and coworkers have had their Charge and Charge HR replaced), and they way, way overestimate caloric expenditure. The Friday before last I told me that I burned 5200 calories. I had walked 31,000+ steps, and lifted, and ran 5k. It was an unusually active day, but there's no chance I blew past 5k calories.