How accurate are the calories reported on heart rate monitors? The one I have knows your weight and heart rate over time. It also may use a measurement of resting heart rate as well but I am not sure about the last.
Not accurate at all. There is simply not enough data for the device to make any accurate measurement of calories expended.
I have a Garmin 305, which I use on bike rides that knows my weight, my heart rate, my speed and distance, and elevation loss/gain. Even with all that data, it is inaccurate - a mountain bike ride that has the same percieved effort as a road bike ride will show less calories burned for the mountain bike ride (presumably because of the lower speed and distance, but I can tell the two rides are roughly the same effort).
A calibrated power meter is what would be accurate. These are available for bicycles but they are not cheap. I’m not sure if they exist for other activities.
I’m with Dag - there are too many additional variables. However, it appears that Polar are the leaders at determining calories expended from heartrate - the latest Garmin GPS training devices all use licensed technology from Polar to determine calorie expenditure from heartrate and GPS information.
Si
It’s a good ballpark estimate.