Someone make a sporttracks plugin that uses this

http://www.ent.ohiou.edu/~et181/hpv/hpv.html is the source for this.

It has been retyped here in plain text

P = p/2(V+Vw)^2 V CdA + (Cr + slope) m g V

m = rider + gear + bike (kg)
V m/s bike velocity
Vw m/s wind (positive if headwind)
P Watts
p 1.18 kg/m^3
CdA m^2 frontal area (A) times coefficient of drag (Cd)
Cr coefficient of rolling resistance = .005 ballpark
slope = elevation/distance
g = 9.81 m/s^2


I weigh about 175 lbs and my bike is 19 or so. Round up for water bottles and call it an even 200 lbs.

200 lb = 90.9kg
CdA = .4 ballpark estimate from the site with the formula -- probably bigger for me

Will have to pull some velocity and slope datapoints from recent rides to see if they check out the same. Climbs should work well because you know you are giving a certain effort there that should be pretty consistent from one ride to the next.