Cycling Power from Speed Calculator

About this calculator

Holding a cycling speed costs power across four physical channels: aerodynamic drag (which dominates at speed and scales roughly with the cube of airspeed), rolling resistance from tire deformation against the road, the gravitational cost of climbing on any gradient, and drivetrain friction losses through the chain and derailleurs. Total power output is simply the sum of these four, and because aero drag depends on the rider's CdA (drag coefficient times frontal area), air density and wind, the same speed can cost very different watts depending on position, equipment and conditions.

Cyclists without a power meter use this breakdown to estimate what a given speed should cost in watts, to sanity-check a power meter's readings, or to see how much of their effort at a given speed is being spent fighting wind versus gravity versus rolling resistance — the split matters for deciding whether an aero upgrade, a lighter bike, or better tires would help more for their typical riding.

This calculator takes your speed, weight, gradient, wind and air density inputs, and returns total power in watts along with the aero, rolling, gravity and drivetrain-loss breakdown.