This instrument is used to measure distances traveled. Its origins go back to late antiquity: it was already described by Vitruvius and, later, Hero of Alexandria. The odometer may be regarded as the ancestor of the modern mileage counter. Many models were designed, of different shapes and sizes. The step-counter version was very small: it consisted of a wheel connected to the ankle by a rod. Thanks to a mechanical system, each complete turn of the wheel was recorded on a dial. A similar system could be connected to a horse saddle or cartwheel.

The odometer designed by Leonardo da Vinci (like the one developed by Leon Battista Alberti) was a device that dropped a pebble in a basket at each complete revolution of the wheel. From the number of pebbles in the basket at the end of the journey, one could compute the distance traveled.

Sixteenth-century odometers usually displayed a recorder dial for calculating the revolutions of the wheel. Instruments similar to odometers are used today to measure distances on maps for comparison with actual distances, to count athletes' steps, to compute mileage traveled, and to determine cyclists' instantaneous speeds.