Cycling Power & Speed

Calculate speed from watts, or estimate climbing time from gradient and power output.

Power (watts) Rider weight

Bike + kit weight (kg) — approx, fixed Gradient (%) Riding position Surface

Speed: —

W/kg: —

How the model works

Power = (gravity force + rolling resistance + aerodynamic drag) × speed

Gravity: mass × 9.81 × gradient. Dominant on steep climbs.

Rolling resistance: Crr × mass × 9.81. Depends on tire and surface.

Aerodynamic drag: ½ × CdA × 1.225 × v². Dominant at high speeds on flat ground.

Speed is found by solving the cubic numerically. Air density assumes sea level, ~15°C.