Cycling power speed estimator
Estimate road cycling speed from rider power, or the power a speed needs, from drag, rolling resistance, gradient and wind. See how much power each resistance takes.
Power 1 to 3,000 W, speed above 0 and up to 108 km/h, rider mass 20 to 250 kg, bike mass 3 to 100 kg, grade -30 to 30%, headwind or tailwind up to 25 m/s (90 km/h), CdA 0.1 to 1.5 m², Crr 0.001 to 0.05, drivetrain efficiency 50 to 100%, altitude -500 to 6,000 m or air density 0.5 to 1.5 kg/m³, ride distance up to 10,000 km. Calculated on your device; download a JSON report and a CSV of results. Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.
Your result
How to use Cycling power speed estimator
- Choose speed from power or power from speed, and enter the power or the speed.
- Enter rider and bike mass, road grade and headwind.
- Adjust drag area, rolling resistance, drivetrain efficiency and altitude or air density if you know them.
- Add a ride distance for time and work, then review the breakdown and download the report.
Useful next steps
The model
Steady road cycling power balances air drag, rolling resistance and gravity: rider power × drivetrain efficiency = (m g sin θ + Crr m g cos θ + ½ ρ CdA (v + w) |v + w|) × v, where θ = arctan(grade) and w is the headwind, so a tailwind faster than the rider pushes. This is the model validated by Martin and others (Journal of Applied Biomechanics, 1998) and written out by Danek, Slawinski and Stanoev (arXiv 2103.09806, March 2021), both checked 16 October 2026. g is 9.80665 m/s² (NIST CODATA 2022).
Assumptions
Speed is steady on a straight road, so acceleration, wheel inertia and bearing losses are left out. Air density from altitude follows ρ = 1.225 × exp(−0.0001186 × altitude in m), from the same paper. CdA, Crr and drivetrain efficiency are your inputs: 0.32 m², 0.005 and 97% are editable examples. With those, 200 W carries a 75 kg rider on a 9 kg bike at about 33.4 km/h on flat road in still air. Speed from power is solved by bisection because power rises steadily with speed.
Limits
Power 1 to 3,000 W, speed up to 108 km/h, rider 20 to 250 kg, bike 3 to 100 kg, grade -30 to 30%, wind up to 90 km/h either way, CdA 0.1 to 1.5 m², Crr 0.001 to 0.05 and altitude -500 to 6,000 m. Results are physics estimates; they say nothing about safe speeds or what a rider can sustain.