How this calculation works
The Cycling Power & Speed Calculator models steady-state cycling velocity by balancing mechanical pedal power (Watts) against aerodynamic air drag (CdA), tire rolling resistance (Crr), gravity, and drivetrain losses.
Mathematical formula and logic
Power = P_aero + P_rolling + P_gravity + P_drivetrain, where P_aero = 0.5 × CdA × Rho × V^3.
Worked example
Producing 200 Watts on flat asphalt (0% gradient) on the brake hoods (CdA 0.32) for an 80 kg rider/bike generates a steady speed of approximately 32.1 km/h (19.9 mph).
Calculation assumptions
- Air density (Rho) standard at sea level = 1.225 kg/m³.
- Coefficient of rolling resistance (Crr) = 0.004 on smooth tarmac; drivetrain efficiency = 97%.
Frequently asked questions
What is CdA in cycling aerodynamics?
CdA is the Coefficient of Aerodynamic Drag (Cd) multiplied by Frontal Surface Area (A). Lowering CdA by riding in the drops or TT aerobars allows you to ride faster at the identical wattage output.
How much speed does an extra 50 Watts provide on flat terrain?
Because aerodynamic drag increases with the cube of velocity (V³), increasing power from 200W to 250W (~25% increase) boosts flat speed from ~32 km/h to ~34.8 km/h (~8.7% speed increase).
What is a good Functional Threshold Power (FTP) for amateur cyclists?
For amateur club cyclists, a typical FTP is 2.5 to 3.5 Watts per kilogram (W/kg). Competitive category racers exceed 4.0 to 4.8 W/kg, and Tour de France pros exceed 5.5 to 6.2 W/kg.
How does body weight affect climbing speed vs flat speed?
On steep climbs (>6%), power-to-weight ratio (Watts/kg) is the dominant performance factor. On flat terrain, absolute power output and aerodynamic CdA dominate.
How many calories does cycling at 200 Watts burn per hour?
At human gross metabolic efficiency of ~24%, riding at 200 Watts for 1 hour burns approximately 720 dietary kilocalories.
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