My garmin wasn't far out after a ride. The next day I did the same ride, similar weather conditions, with the doc's HRM and tracker do-dah on. There was about 40 calories difference. I do keep my weight up to date with the Garmin, both on the website and on the device itself. It's not like I use the calorie infomation for anything. I don't decide to eat back the caloried burned.