Sports

Cycling Wattage Calculator

Estimate the power needed to ride at a given speed.

Rider + bike weight

Speed

Gradient (%)

Rolling resistance Crr

Drag area CdA

Calculated Output

Power required (W) 139.04

Formula: P = (F_roll + F_grav + F_aero) × v

Step-by-Step Breakdown

1. Values used:

2. Rider + bike weight = 80

3. Speed = 30

4. Gradient = 0 %

5. Rolling resistance Crr = 0.005

6. Drag area CdA = 0.3

8. Power required = 139.04W

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The math behind it

P = (F_rolling + F_gravity + F_aero) × speed. Aerodynamic drag dominates at higher speeds.

80 kg at 30 km/h on the flat → about 165 W.

Why does drag matter so much?

Aero force grows with the square of speed, so it dominates above ~25 km/h.