Cycling Power from Speed Calculator

How it is calculated

This is the basic force-times-velocity relation: P = F × v. F is the total resisting force you must overcome, in newtons, and v is your speed in m/s. You type speed in km/h and the tool converts it with v = km/h ÷ 3.6. The answer is power at the wheel in watts, shown with two decimals. You supply F yourself: it is the sum of air drag, tyre rolling resistance and, on a slope, the pull of gravity, and the tool does not work these out from weight, CdA or grade. Both fields must be above 0, speed up to 300 km/h and force up to 3,000 N, and a resulting power above 5,000 W is treated as beyond any human cyclist and gives no result. Drivetrain loss is not added.

Common mistakes

• Entering the rider's weight as the resistance. The field wants a force in newtons, not kilograms. A weight of 80 kg is not 80 N, and it is not the net resistance on the bike either.
• Using a resistance measured at a different speed. Air drag grows with the square of speed, so a force taken at 20 km/h understates the force at 40 km/h.
• Typing speed in m/s or mph. The field is km/h, so 10 m/s must be entered as 36.
• Expecting the tool to add climbing, wind or drivetrain loss. It only multiplies two numbers, so any slope or headwind must already be inside the force you enter.
• Entering a zero or negative force for a descent or tailwind. The tool returns no result in that case.