Accuracy of calories burned while biking

[Crankin]

This is why I stopped using technology on my rides. I was getting obsessed with the numbers and jealous when people were higher/lower/blah, blah, blah. And, I found I was constantly looking at my monitor, which was not good.
I didn't learn anything that I already knew. 1) My HR is always higher than others of the same weight/height/age, despite the fact I have been fit for 25 years 2) At my size, it is incredibly hard to burn calories. I have to work twice as hard or ride three times as long to burn the same number of calories as someone who is of average height and heavier. Even when I was 32, weighed 90 lbs. and was teaching 7 fitness classes a week, my average HR was high during a work out. Since I don't have any cardiac issues, I assume it's just the way my body works.
So, I figure when I am breathing heavy at the top of a 15% grade, that is my cue that I am working hard. I also use my average speed or time over routes that I do all of the time to judge how my fitness progresses over the season.

[goldfinch]

There are too many variables for the Garmin to give accurate readings. It uses your heart rate and algorithms to make estimates but does not account for all variables, like percentage of body fat.

But then again, estimates of calories eaten aren't so accurate either.

Typically, these heart rate monitor estimates are high. But as others mentioned you will get a low estimate if your heart rate is artificially measured low.