Calculateur de Puissance de Cyclisme — Formule

How Cycling Power Is Estimated

Power required to cycle comes from three main sources: aerodynamic drag, rolling resistance, and gravity.

Formula

Total Power = P_aero + P_rolling + P_gravity

  • P_aero = 0.5 x air density x CdA x v^3 (CdA assumed 0.32 x 0.88)
  • P_rolling = Crr x mass x g x v (Crr assumed 0.005)
  • P_gravity = mass x g x gradient x v

    • Where v is speed in m/s, g is 9.81 m/s^2.

    Key Insight

    Aerodynamic drag increases with the cube of speed, so doubling your speed requires roughly 8 times the power to overcome air resistance.

    Exemple Résolu

    Riding at 18 mph on flat road, 185 lbs total rider+bike weight.

    1. Speed = 18 * 0.44704 = 8.05 m/s
    2. Mass = 185 * 0.4536 = 83.9 kg
    3. P_aero = 0.5 * 1.225 * 0.2816 * 8.05^3 = 90.0 W
    4. P_rolling = 0.005 * 83.9 * 9.81 * 8.05 = 33.1 W
    5. P_gravity = 0 (flat road)
    6. Total = 90 + 33 + 0 = 123 W
    7. W/kg = 123 / 83.9 = 1.47 W/kg