Leonardo da Vinci designed an odometer that measured distance by counting wheel rotations.
The machine used a large wheel connected to a gear train and a counting mechanism. As the wheel traveled over the ground, each rotation advanced the counter. A container could release a small stone at set intervals, allowing the operator to estimate the distance covered by counting the stones collected.
Leonardo’s design belongs to his wider interest in precise mechanical measurement. Surveyors and engineers needed distances for roads, canals, fortifications, and construction, but measuring long routes by repeatedly laying out a rod was slow. A wheel-based counter offered a practical alternative.
An odometer measures distance, not speed. That distinction is important because a speedometer shows how fast something is moving at a particular moment. Leonardo’s device was a mechanical measuring concept rather than a modern vehicle dashboard instrument, and it was designed for travel over land.