Foot (unit)
The foot (symbol: ft) is a unit of length used in the British imperial and US customary systems. It is often represented by the prime symbol (′). One foot equals 12 inches, and three feet make a yard. Since a 1959 international agreement, the foot has been defined as exactly 0.3048 meters. The usual plural is "feet," but the singular "foot" can follow a number, as in "six foot tall." Informally, "footage" refers to a length in feet.
Historically, the foot appeared in many local systems, including Greek, Roman, Chinese, French, and English ones. Its length varied by country, city, and even trade, typically ranging from about 250 mm (9.8 in) to 335 mm (13.2 in). It was usually divided into 12 inches or 16 digits.
The US is the only industrialized country that uses the international foot over the meter for many commercial, engineering, and standards activities. The UK legally recognizes the foot; road signs use imperial units (miles or yards, not feet), and bridge clearances are given in meters as well as feet and inches. The foot is widely used by the British public for height. Canada accepts the foot as an alternative length expression. Both the UK and Canada have partially metricated their measurements. International aviation uses the foot for altitude (flight levels), one of the few non-English-speaking contexts where it appears.
**Historical origin**
The human body historically provided the basis for length units. An adult European-American male's foot is typically about 15.3% of his height, so a 175 cm (5 ft 9 in) person has a foot length around 268 mm (10.6 in). Archaeologists believe ancient Egyptians, Indians, and Mesopotamians preferred the cubit, while Romans, Greeks, and Chinese preferred the foot. Indus cities during the Bronze Age used a foot of 13.2 inches (335 mm) and a cubit of 20.8 inches (528 mm). The Egyptian foot—four palms or 16 digits, called the djeser—has been reconstructed at about 30 cm (11.8 in).
The Greek foot (pous) was 1/600 of a stadion (about 181.2 m or 594 ft), making it about 302 mm (11.9 in). Its size varied by city, from 270 mm (10.6 in) to 350 mm (13.8 in), but temple construction lengths were roughly 295 mm (11.6 in) to 325 mm (12.8 in). The standard Roman foot (pes) was about 295.7 mm (11.6 in), though in some provinces, like Germania Inferior, the pes Drusianus (about 334 mm or 13.1 in) was used; this foot predated Drusus. Both Greeks and Romans originally divided the foot into 16 digits, but the Romans later used 12 unciae (source of "inch" and "ounce"). After the Roman Empire fell, some traditions continued while others faded. In 790, Charlemagne tried to reform units, basing lengths on the toise (the distance between a man's outstretched fingertips). The toise had 6 pieds (feet) of 326.6 mm (12.9 in), but he failed to standardize across his realm: Charlieu Abbey used the Roman foot of 296.1 mm (11.66 in) in the 9th century, a foot of about 320 mm (12.6 in) in the 10th century, and monastic buildings used the Carolingian foot of 340 mm (13.4 in).
A 16th-century method for verifying the foot, described by Jacob Köbel, instructed: stand at a church door on a Sunday, bid 16 men (tall and short) to stop as they leave, have them place their left feet one behind the other, and the total length is a lawful rood; its 16th part is the lawful foot.
**England and Wales**
Archaeologists Mike Parker Pearson and Andrew Chamberlain proposed a Neolithic long foot based on surveys of Stonehenge’s Phase 1 elements. The stone circles’ diameters were consistently laid out in multiples of 30 long feet, each equal to 1.056 of a modern international foot (12.672 inches or 0.3219 m). This unit appears in some stone lintels at Stonehenge and in the diameter of the "southern circle" at Durrington Walls. Evidence of its widespread use in southern Britain comes from the Folkton Drums (Yorkshire Neolithic chalk artifacts with circumferences dividing exactly into ten long feet) and the Lavant drum (from Lavant, Sussex), also with a circumference divisible into ten long feet. Iron Age British measures are uncertain, and reconstructions like the megalithic yard are debated. Later Welsh legend credited Dyfnwal Moelmud with establishing units, including a foot of 9 inches.
- Type
- Unit of length
- Systems
- British imperial, US customary
- Symbol
- ft, ′
- Subunits
- 12 inches per foot, 3 feet per yard
- Notable usage
- Altitude in international aviation
Quick Facts
- Symbol
- ft
- Standard
- Imperial/US units
- Quantity
- Length
- Units2
- Metric (SI) units
- Inunits2
- 0.3048 m · 30.48 cm · 304.8 mm
- Inunits1
- 3 yd · 12 in
Facts from the source article.
Lore & Background
Historically, the foot was a unit of length in many local systems, including those of the Greeks, Romans, Chinese, French, and English, with its length varying widely between countries, cities, and even trades. Its value usually fell between certain limits and was generally, though not always, divided into twelve inches or sixteen digits. The human body often provided the basis for these units; for instance, the foot of an adult European-American male is typically about 15.3% of his height. In ancient times, the Egyptians, Indians, and Mesopotamians preferred the cubit, while the Romans, Greeks, and Chinese favored the foot. The Indus Valley civilization used a foot of a specific length during the Bronze Age, and the Egyptian equivalent, known as the *djeser*, measured four palms or sixteen digits. The Greek foot varied by city but was roughly a fraction of a stadion, while the standard Roman foot was normally about a certain length, though a variant called the *pes Drusianus* was used in some provinces. After the Roman Empire’s fall, Charlemagne attempted to standardize units in 790, basing his lengths on the *pertica* and the *ulna*, but his reforms were not uniformly adopted; for example, a 9th-century abbey used the Roman foot, while a 10th-century rebuild used a different foot, and monastic buildings employed the Carolingian foot. A 16th-century procedure for verifying the foot, described by Jacob Köbel, involved sixteen men leaving church and placing their left feet one behind the other, with one sixteenth of that total length deemed the lawful foot. In Neolithic Britain, a "long foot" of 1.056 modern international feet has been proposed based on surveys of Stonehenge and other sites, with artifacts like the Folkton Drums and Lavant drum showing circumferences divisible into ten such feet. Later, the Belgic or North German foot was introduced to England, and after the Roman conquest, the Roman foot continued in construction while the Belgic foot was used for land measurement.
Reader's Guide
The foot remains a significant unit of length in the United States for many commercial, engineering, and standards activities, and is legally recognized in the United Kingdom and Canada. Its definition was standardized internationally in 1959, ending centuries of variation. The foot's historical importance is evident in its use across multiple ancient civilizations, including Greek, Roman, Chinese, and English systems, where it was often subdivided into 12 inches or 16 digits. The foot's persistence in aviation altitude measurement demonstrates its continued relevance beyond the English-speaking world. The transition from diverse local definitions to a single international standard reflects broader efforts toward measurement harmonization, though the United States remains the only industrialized country to prefer the foot over the meter in many contexts.
Did You Know?
- A 16th-century method for verifying the foot involved 16 men placing their left feet one behind the other after church.
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