Welcome to Bike Forums. Sometimes a newbie will ask a question that just explodes with a lot of tangents. You have done exactly that. Whenever I did that three years back, I always felt proud.

I have read a LOT on this subject (I am fat) and I find that 500 calories per hour for "working pretty hard" seems to agree with most of the pundits. So your 1:20 ride probably used about 666 calories. As someone noted above, different monitors and analytic tools give wildly divergent numbers - I consider the number that my Garmin generates is useless. Obviously, as indicated by the responses, there is a lot of variability. As you ride more, you will become more efficient, meaning you burn less calories on the same course at the same speed. But as that happens, you will automatically start riding faster - maybe in two months you will ride your 17.32 mile course in one hour flat, and that would use about 500 calories.

But let me note that some of the people responding are very, very knowledgeable. As you read the answers, note how some people seem to know a little more and respond to challengers with consideration. Those are the people I pay the most attention to.

Congratulations on your riding and good luck with your weight loss. Do everything possible to enjoy your riding - scenic routes, good company (join a cycling club*?), comfortable clothing - so you continue to ride. Quite a number of people say that riding before breakfast burns more calories (I don't know if it's true, but I often do it).


* I joined two clubs the first month I started riding. I learned much faster as a result - what to wear, etiquette, scenic courses, etc. I rode in an organized ride almost every Wednesday (mostly retired riders), Saturday, and Sunday for the first six months.