Air Resistance Power Calculator

How it is calculated

The tool computes only the power spent on pushing through the air: P = ½ × ρ × CdA × v³. Here ρ is air density in kg/m³, CdA is drag coefficient times frontal area in m², and v is speed in m/s. You enter speed in km/h, and the tool converts it with v = km/h ÷ 3.6. All three fields are required and must be above 0. Values that are physically absurd (CdA above 50 m², density above 3 kg/m³, speed above 1,500 km/h) show no result. The speed is treated as speed through the air, so there is no wind input: for a headwind add the wind speed to your ground speed, for a tailwind subtract it. Rolling resistance, climbing and drivetrain loss are not included, so this is only the aero part of total power.

Common mistakes

• Entering CdA in cm² or as the frontal area alone. The field is the product in square metres, commonly a few tenths such as 0.32, so 3200 would be wrong by a factor of 10,000 (and is rejected as above 50).
• Treating the result as total power. It excludes rolling resistance, gravity and drivetrain loss, so a rider's real power on the road is higher.
• Ignoring wind. The speed must be airspeed: with a 10 km/h headwind and 30 km/h ground speed, enter 40.
• Using the sea-level density at altitude or on a hot day. The air density field takes your actual value, and 1.225 kg/m³ only applies to roughly 15 °C at sea level.
• Expecting a linear scale. Speed is cubed, so a 10 % speed increase costs about 33 % more aero power, not 10 %.