Determination of the rod, using the length of the left foot of 16 randomly chosen people coming from church service. Woodcut published in the book Geometrei
by Jakob Köbel
(Frankfurt, c. 1535).
Historically the human body has been used to provide the basis for units of length. The foot of a white male is typically about 15.3% of his height, giving a person of 160 centimetres (5 ft 3 in) a foot of 245 millimetres (9.6 in) and one of 180 centimetres (5 ft 11 in) a foot of 275 millimetres (10.8 in).
Archaeologists believe that the Egyptians, Ancient Indians and Mesopotamians preferred the cubit while the Romans and the Greeks preferred the foot. Under the Harappan linear measures, Indus cities during the Bronze Age used a foot of 13.2 inches (340 mm) and a cubit of 20.8 inches (530 mm). The Egyptian equivalent of the foot—a measure of four palms or 16 digits—was known as the djeser and has been reconstructed as about 30 cm (12 in).
The Greek foot (πούς, pous) had a length of 1⁄600 of a stadion, one stadion being about 181.2 m, therefore a foot being at the time about 302 mm. Its exact size varied from city to city and could range between 270 mm and 350 mm, but lengths used for temple construction appear to have been about 295 mm to 325 mm, the former being close to the size of the Roman foot.
The standard Roman foot (pes) was normally about 295.7 mm (97% of today's measurement), but in the provinces, the pes Drusianus (foot of Nero Claudius Drusus) was used, with a length of about 334 mm. (In reality, this foot predated Drusus.)
Originally both the Greeks and the Romans subdivided the foot into 16 digits, but in later years, the Romans also subdivided the foot into 12 unciae (from which both the English words "inch" and "ounce" are derived).
After the fall of the Roman Empire, some Roman traditions were continued but others fell into disuse. In AD 790 Charlemagne attempted to reform the units of measure in his domains. His units of length were based on the toise and in particular the toise de l'Écritoire, the distance between the fingertips of the outstretched arms of a man. The toise has 6 pieds (feet) each of 326.6 mm (12.86 in).
He was unsuccessful in introducing a standard unit of length throughout his realm: an analysis of the measurements of Charlieu Abbey shows that during the 9th century the Roman foot of 296.1 mm was used; when it was rebuilt in the 10th century, a foot of about 320 mm[Note 1] was used. At the same time, monastic buildings used the Carolingian foot of 340 mm.[Note 1]
The procedure for verification of the foot as described in the 16th century posthumously published work by Jacob Koebel in his book Geometrei. Von künstlichem Feldmessen und absehen is:
Stand at the door of a church on a Sunday and bid 16 men to stop, tall ones and small ones, as they happen to pass out when the service is finished; then make them put their left feet one behind the other, and the length thus obtained shall be a right and lawful rood to measure and survey the land with, and the 16th part of it shall be the right and lawful foot.
The Neolithic long foot, first proposed by archeologists Mike Parker Pearson and Andrew Chamberlain, is based upon calculations from surveys of Phase 1 elements at Stonehenge. They found that the underlying diameters of the stone circles had been consistently laid out using multiples of a base unit amounting to 30 long feet, which they calculated to be 1.056 of a modern foot (0.3219m). Furthermore, this unit is identifiable in the dimensions of some stone lintels at the site and in the diameter of the "southern circle" at nearby Durrington Walls. Evidence that this unit was in widespread use across southern Britain is available from the Folkton Drums from Yorkshire (neolithic artifacts, made from chalk, with circumferences that exactly divide as integers into ten long feet) and a similar object, the Lavant drum, excavated at Lavant, Sussex, again with a circumference divisible as a whole number into ten long feet.
The measures of Iron Age Britain are uncertain and proposed reconstructions such as the Megalithic Yard are controversial. Later Welsh legend credited Dyfnwal Moelmud with the establishment of their units, including a foot of 9 inches. The Belgic or North German foot of 335 mm (13.2 inches) was introduced to England either by the Belgic Celts during their invasions prior to the Romans or by the Anglo-Saxons in the 5th and 6th century.
Roman units were introduced following their invasion in AD 43. The had been previously standardized by Agrippa at around 296 mm or 11.65 inches. Following the Roman withdrawal and Saxon invasions, the Roman foot continued to be used in the construction crafts while the Belgic foot was used for land measurement. Both the Welsh and Belgic feet seem to have been based on multiples of the barleycorn, but by as early as 950 the English kings seem to have (ineffectually) ordered measures to be based upon an iron yardstick at Winchester and then London. Henry I was said to have ordered a new standard to be based upon his own arm and, by the c. 1300 Act concerning the Composition of Yards and Perches traditionally credited to Edward I or II, the statute foot was a different measure exactly 10⁄11 of the old foot. The barleycorn, inch, ell, and yard were likewise shrunk, while rods and furlongs remained the same. The ambiguity over the state of the mile was resolved by the 1593 Act against Converting of Great Houses into Several Tenements and for Restraint of Inmates and Inclosures in and near about the City of London and Westminster, which codified the statute mile as comprising 5,280 feet. The differences among the various physical standard yards around the world, revealed by increasingly powerful microscopes, eventually led to the 1959 adoption of the international foot defined in terms of the meter.