I just did a calculation based on my weight (229 lbs) that indicated that cycling at 14-16 mph would burn 1374 calories per hour. My ride today was 31 miles at 15.2 mph. I've walked on a treadmill and tried to burn 1000 calories per hour. I'm completely wasted after 2 hours. But 2 hours on the bike at the pace mentioned above and I feel fine. The bicycling calculation is from thedailyplate.com.