Cycling Power Calculator
Estimate the watts needed to ride at a given speed, with your weight, gradient, wind and riding position.
About the Cycling Power Calculator
Cycling power goes into overcoming air resistance, gravity on climbs and tyre rolling resistance. On the flat above about 20 km/h, air drag dominates and rises with the cube of speed, which is why an aero position saves so much.
The formula
P = (Crr·m·g·cos θ + m·g·sin θ + ½·ρ·CdA·v²) × v ÷ 0.975
- Crr
- 0.005 (good road tyres)
- ρ
- 1.225 kg/m³ air density at sea level, 15 °C
- CdA
- 0.23–0.40 m² by position
- 0.975
- 2.5% drivetrain loss
Worked example
Example: Power needed = 198 W
- Inputs: Rider weight: 83 kg; Bike and kit: 10 kg; Speed: 33 km/h; Gradient: 0%; Headwind (negative for tailwind): 0 km/h; Riding position: Hoods (road bike).
- Formula: P = (Crr·m·g·cos θ + m·g·sin θ + ½·ρ·CdA·v²) × v ÷ 0.975
- Result: Power needed = 198 W
Questions people ask
What's a typical FTP?
Recreational riders often hold 2–3 W/kg for an hour; strong amateurs 4 W/kg or more.
Why does speed cost so much?
Air-drag power rises with speed cubed: going 10% faster needs about 33% more power on the flat.