Leonardo da Vinci designed an odometer to estimate distance traveled by a wheel.
His design used a wheel with a known circumference and a counting mechanism. As the wheel turned, gears transferred its rotation to a series of numbered dials or containers. Counting the completed turns made it possible to calculate how far the device had traveled.
The principle is straightforward: distance equals the number of wheel rotations multiplied by the wheel’s circumference. Leonardo’s version was intended for surveying and mapping, where measured travel could help establish distances along roads or terrain. It was a mechanical measuring instrument rather than a vehicle dashboard device.
Leonardo’s odometer should not be confused with a speedometer. An odometer measures accumulated distance, while a speedometer measures the rate of travel. The device also belongs to a much older tradition: ancient engineers had already developed distance-measuring instruments, but Leonardo’s drawings show his characteristic interest in compact gears and automatic counting.