Wheel Size Speed Calculator

About this calculator

This calculator converts a wheel's circumference and its rotational speed in RPM (revolutions per minute) into linear travel speed, using the relationship speed = circumference × RPM × 60 (converted to km/h or mph). Circumference itself is usually derived from wheel diameter using C = π × diameter, so the same formula works for anything from a bicycle wheel to a go-kart or scooter tire.

Cyclists and bike-computer manufacturers use this exact relationship to calibrate speed sensors: a magnet-based cadence/speed sensor counts wheel revolutions, and the device multiplies that count by the rider's specific wheel circumference (which varies by tire size, e.g., 700x25c vs 26-inch) to display accurate speed. Engineers designing small vehicles, robotics, and motorized wheelchairs use the same math to translate a motor's RPM output into real-world travel speed.

This calculator takes your wheel's circumference and its RPM and returns your speed in both km/h and mph, so you can cross-check a bike computer reading or size a wheel/motor combination for a target speed.