Originally Posted by bruce19

This interests me just 'cause I like stuff like this. I don't have a power meter but I do post on Garmin, Strava and a site called FitDay - Free Weight Loss and Diet Journal. In addition, I have in the past used formulas from various on line sites that are associated with places like the Mayo Clinic and other medial organizations. And, I have a couple books on the subject including ones that address training issues for older athletes. All of them take into consideration age, gender, weight, effort (including mph and climbing) and using a variety of them always yields results that are fairly similar. Here's an example for the 50 mi. ride I referenced. This was 50 mi. w/3,000 of elevation at 14.5 mph. As I recall, riding time was around 3:15. And, my personal data would be Male, 70 yrs. old at 190 lbs. Calories burned according to :

Garmin...2995
Strava...2847
FitDay... 2884

This tracks pretty closely with the formulas I've gotten in books and on line. So, compared to using a power meter all of these can be off in a major way?