Leonardo da Vinci designed an odometer to measure distance using a wheel and a gear mechanism.
As the wheel turned, its movement could be transferred through gears to a counting display. Each rotation represented a known distance, allowing the device to record how far a cart or vehicle had traveled.
Leonardo’s design belongs to a long history of mechanical distance measurement. Ancient Greek engineers had already developed related devices, but Leonardo studied and redrew such mechanisms in Renaissance notebooks. His version is often discussed as an early mechanical odometer, not as the inventor of the general idea.
A common mix-up is confusing an odometer with a speedometer. An odometer records total distance, while a speedometer measures speed. Leonardo’s design was concerned with accumulated distance rather than instantaneous velocity.