how many calories do you burn when riding bicycle?. Is there a formula based on weight, average speed, time?.?

Answer 1

some heart rate monitors will calculate calories burned. it may be off by a couple percent but it will give you an idea.

for me 180lbs on a good road bike:
recovery (slow 14mph) about 400 to 500 for an hour
fast (race or hard group ride) up to 1000+ an hour

Answer 2

Go to fitday.com. You can put in your excerise, your food intake and get answers to exactly what you have burned vs. what you have eaten and more. It's a great site!