Convert roman foot to yard

The inch has been exactly 2.54 cm since 1959; 12 inches make a foot, 3 feet a yard and 1,760 yards a mile of 1.609 km. The US and UK still use them for heights (5 ft 10 in is 178 cm), road distances and speed limits, and the inch survives everywhere in screen sizes, wheel rims and pipe threads. Five miles are almost exactly eight kilometres, a handy road-sign rule.

Roman lengths were built on the foot (pes, about 29.6 cm): 16 digiti (finger widths) or 4 palmi (palm widths) made a foot, 1½ feet a cubit, 5 feet a passus (a double step), 10 feet a pertica (perch) and 120 feet an actus, the length of a furrow. Longer distances counted in stadia of 625 feet and in mille passuum, a thousand double steps or 5,000 feet, which is where the word mile comes from; the Gallic leuga was 1½ Roman miles. Milestones along the Roman roads were set one mille passuum apart.