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Cycling Speed From Power Calculator

Work out cycling speed from power instantly with clear inputs, formula shown and shareable results.

About Cycling Speed From Power Calculator

Speed follows from balancing power against aerodynamic drag, rolling resistance, gradient and drivetrain loss. Because drag grows with the cube of speed the equation must be solved numerically, which this calculator does by Newton iteration. At 200 W with CdA 0.32 on the flat, a rider holds about 32 km/h, with roughly 80% of the power going into pushing air aside.

Formulas

Power balance

P x drivetrain = 0.5 rho CdA v^3 + Crr m g v + m g v x grade

Drag power

P(air) = 0.5 rho CdA v^3

Worked example

With the default values below, Cycling Speed From Power Calculator returns Predicted Speed of 30.97. Change any input above and every figure here is recalculated in your browser.

Inputs used

Power outputminimum 0 W
200 W
Rider plus bike weightminimum 1 kg
82 kg
Drag area CdAminimum 0.05 m2
0.32 m2
Gradientaccepts -15–20 %
0.5 %

Results

Predicted Speed
30.97 km/h
Same Speed In Metres Per Second
8.603
Power Lost To Air Resistance
124.8 W
Power Lost To Rolling Resistance
34.59 W

Step by step

  1. 1Values used
  2. 2Power balance
  3. 3Drag power
  4. 4Predicted Speed= 30.97 km/h
  5. 5Same Speed In Metres Per Second= 8.603
  6. 6Power Lost To Air Resistance= 124.8 W
  7. 7Power Lost To Rolling Resistance= 34.59 W

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • This is an estimate from population-average equations, not a medical or diagnostic assessment. Individual results vary with genetics, training history and technique. Seek advice from a qualified coach or clinician before making significant changes to training.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

This is an estimate from population-average equations, not a medical or diagnostic assessment. Individual results vary with genetics, training history and technique. Seek advice from a qualified coach or clinician before making significant changes to training.

Frequently Asked Questions

Why does aerodynamics dominate on the flat?

Because drag power rises with the cube of speed. Above about 25 km/h it is the majority of your output, which is why position matters more than weight.

What CdA should I use?

About 0.4 upright on the hoods, 0.32 on the drops, 0.28 in the drops with aero kit and 0.22 or lower in a full time-trial position.

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