CYCLING PERFORMANCE TIPS 
Where:
ASSUMPTIONS
BICYCLE WT
RIDER + GEAR
K1 K2

MTN BIKE
15 kg
80 kg
7.845 0.3872

ROAD BIKE
10 kg
75 kg
3.509 0.2581

*Cv is your AIR speed (ie the resistance you are pedalling against is the resistance of the air to your body and bike as you ride) and is not the GROUND speed off your computer. So if there is a head wind, add that speed to your ground speed to determine the velocity for this formula. And if it is a tail wind, subtract it from your ground speed. If you think about it, this makes sense  it is always easier to ride with a tail wind. This formula quantitates how much easier.
**The constants K1 and K2 are for a road rider/bicycle/gear of 85 kg (187 lbs) or mountaion bike/rider/gear of 95 kg (210 pounds) . If you need to be more specific, the original derivation is referenced at the top of this page. But biking is NOT an exact science, and this formula will at least get you into the right ballpark.
If you want the energy expended at the pedal in Calories/min:
As the body is only 25% efficient at best in converting Calories eaten into Calories delivered as power output, the number of Calories that would need to be eaten per minute to sustain a speed of Cv mph would be:
So if you know the average speed (velocity) of your ride, and the total time you were out, you can calculate the number of Calories "burned". Here are a few examples (average speed for the ride, on the flats):