Cycling Wattage Calculator
Estimate the power output (in watts) needed to ride at a given speed based on your weight, the road grade, and basic aerodynamics.
What this calculator does
It estimates the power (in watts) a cyclist needs to sustain a given speed, combining the three main physical forces a rider must overcome: gravity (on a climb or descent), rolling resistance between tires and road, and aerodynamic drag from the air.
The formula
Power is calculated as Power = (Gravity Force + Rolling Resistance Force + Aerodynamic Drag Force) × Speed ÷ Drivetrain Efficiency. Aerodynamic drag force uses the standard formula 0.5 × air density × CdA × speed², where CdA (drag area) is estimated from your riding position — a more aerodynamic tuck substantially reduces the power needed at higher speeds.
Rolling resistance assumes a typical road tire coefficient (Crr ≈ 0.005), and drivetrain losses assume a well-maintained chain (about 2.5% loss). Real-world numbers vary with tire choice, bike fit, wind, altitude, and drivetrain condition.
This tool is for general training and reference purposes; it is not a substitute for a calibrated power meter.