My Garmin 705 has the infamous "way off" calorie calculation even using the HRM. For a 25 mile ride it states I burn 2600 cals. Thats 104 cals per mile. I usually half whatever the device reports and Im somewhere close.
Originally Posted by
engstrom
I use my Garmin 800 as kind of a rough gauge of how many calories I've burned. When I first got the Garmin (I didn't buy the complete package because I wanted a different speed/cadence sensor) the calorie count was way overestimated. Now that I've got a HRM to go with it the calorie count is in the ballpark. I still won't use it as an excuse to eat more, but it's nice to have a rough idea of work done on a ride without the expense of a power meter.
My last ride was 36.5 miles with an average heart rate of 73% of my maximum heart rate and 1,137 calories burned. That's ~31 calories per mile which fits right in WonderMonkey's 20-45 calories per mile.