Cycling Speed from Power Calculator

About this calculator

Cycling speed at a given power output is governed by the balance between the watts you produce and the forces resisting you: aerodynamic drag (a function of your CdA — frontal area times drag coefficient — and air density), rolling resistance from tires and road surface, and gravity acting against your combined bike-and-rider weight on any grade, with altitude further reducing air density and therefore drag. Solving this power-balance equation for speed, rather than the more common speed-to-power direction, tells you how fast a given wattage will actually carry you under real conditions.

Cyclists using power meters, and coaches planning pacing strategies for climbs, time trials or flat stages, use this calculation to translate a target or sustainable power number into an expected speed, accounting for how much a climb, a headwind-equivalent CdA, or a high-altitude course will slow them down compared to a flat sea-level ride at the same wattage.

This calculator takes your power output, grade, weight, CdA, rolling resistance and altitude, and returns the speed those watts will actually produce under those conditions.