Biking equations
 

Okay so today I went for an 18 mile bike ride, and I clocked myself at about 4 minute miles. I was wondering if there is some sort of equation to figure out how many calories burned during your workout.

Figure (very) roughly 25-40 calories a mile. Speed is less important than other factors, such as rider & bike weight, hills and wind. If you do a google search, I think you'll find some calculators. Not sure how accurate they are.

If you're not doing any big climbs I would estimate under 30 Cals/Mile for 15mph speed.

Approx 500-600 calories per hour.

how fast do you ride and how much do you weigh? I would say unless you are riding upwards of 19mph (which is around 200 watts) for most normal weight people, 30/mile is a larger over estimate. I'd say go more around 20-23/mile especially if you are trying to lose weight.

19MPH and 200W is about 38 Cals/mile. 20 Cals/mile and 15MPH would require only 83W. I think if you just lift your legs and let them fall on the pedals you generate around 150W.

I weigh 165 and the lowest Cals/mile I've recorded is 29/mile @ 143W and 17MPH for a mostly flat recovery ride.