One sixteenth of sixteen churchgoers' feet was once a lawful foot
A sixteenth-century German surveying manual by Jacob Köbel offered a practical recipe. After Sunday service, stop sixteen men leaving church, tall and short alike, and have them line up their left feet heel to toe. That total made a lawful rod for measuring land, and one sixteenth of it served as the foot.
Averaging a crowd made sense because feet, like the units named after them, varied enormously. Historic feet ranged from about 250 to 335 millimetres, differing between countries, cities and even trades. The Greek foot was one six-hundredth of a stadion, roughly 302 millimetres, while the standard Roman one was about 296 and was later split into twelve unciae, the root of both inch and ounce. Charlemagne tried to impose a single standard in 790 and failed; one abbey's buildings show a Roman foot in the ninth century and a longer one after its rebuilding in the tenth.
Some claims reach much further back. Archaeologists Mike Parker Pearson and Andrew Chamberlain argue that the builders of Stonehenge laid out its stone circles using a Neolithic long foot slightly larger than today's, and that the same unit fits the carved chalk Folkton Drums from Yorkshire. In England, the Roman foot lingered in building trades while a longer Belgic foot measured land, until a statute around 1300 set the official foot at exactly ten-elevenths of the old Belgic one. A 1593 act fixed the mile at 5,280 feet.
The modern foot is a metric creation. A 1959 international agreement defined the yard as exactly 0.9144 metres, making the foot 0.3048 metres, a whisker shorter than the previous American definition and a touch longer than the British. Surveyors had a problem, though: vast amounts of US land data already used the older survey foot, and over the huge distances of state coordinate grids, those parts-per-million added up. The US survey foot was formally deprecated only at the end of 2022.
Today the United States is the only industrialised country that prefers the foot over the metre in much commercial and engineering work. Britain still uses feet widely for height, and pilots worldwide measure altitude in feet, one of the few places the unit appears outside the English-speaking world. An adult man's foot, incidentally, averages about 15 percent of his height.
Source: Foot (unit)
