Originally Posted by canam73

Not by my results.

I use a KK Road machine with a quarq or PT and ride outside with both. Comparing some trainer and solo road rides with an average speed of ~20 mph I get a power meter reading composite of around 239 watts whether indoor or out. If my math is right the above formula would predict 258w for a error of around 8%. And fwiw, I weigh 175, calibrate or zero before every ride and probably do solo rides at around 70% hoods/25% drops.