Foot (unit)
Archaeologists examining Stonehenge found that the stone circles were laid out using multiples of a base unit called the long foot. This ancient measure calculated to 12.672 inches or 0.3219 meters. It appears in dimensions of stone lintels at the site and in the diameter of the southern circle nearby. Evidence for this unit exists across southern Britain from Folkton Drums made of chalk. These drums have circumferences that divide exactly into ten long feet. A similar object known as the Lavant drum was excavated at Lavant, Sussex with matching properties.
The human body provided the original basis for these units before standardization arrived. An adult European-American male typically has a foot length equaling about 15.3% of his total height. People in Egypt, India, and Mesopotamia preferred the cubit while Rome, Greece, and China favored the foot. The Egyptian foot measured four palms or 16 digits and reconstructed to approximately 296 millimeters. Greek feet varied significantly from city to city ranging between 280 and 340 millimeters. Temple construction often used lengths between 295 and 305 millimeters.
Roman standards differed by region. The standard Roman foot measured roughly 296 millimeters but provinces like Germania Inferior used the foot of Nero Claudius Drusus. This specific variant reached about 297 millimeters though it predated Drusus himself. Both Greeks and Romans originally divided their feet into 16 digits. Later Romans subdivided the foot into 12 inches which gave rise to English words inch and ounce.
Neolithic long feet first proposed by archaeologists Mike Parker Pearson and Andrew Chamberlain emerged from calculations on Phase 1 elements at Stonehenge. They discovered underlying diameters consistently laid out using multiples of 30 long feet. This unit identified itself in dimensions of stone lintels and the diameter of the southern circle at Durrington Walls. Evidence for widespread use across southern Britain comes from Folkton Drums found in Yorkshire. These chalk artifacts have circumferences dividing as integers into ten long feet.
Iron Age British measures remain uncertain with controversial reconstructions like the megalithic yard. Welsh legend credited Dyfnwal Moelmud with establishing units including a foot of nine inches. Belgic or North German feet measuring 11 inches entered England via Belgic Celts before AD 43 or Anglo-Saxons during the fifth and sixth centuries. Roman units followed conquest while Roman feet continued in construction crafts after withdrawal. The Belgic foot served land measurement purposes.
Both Welsh and Belgic feet derived from barleycorn multiples yet English kings attempted standardization by 950. Henry I ordered new standards based on his own arm length. Edward I enacted legislation traditionally crediting him or Edward II creating the statute foot. This measure differed exactly from the old Belgic foot. Barleycorn, inch, ell, and yard shrunk while rods and furlongs remained unchanged. Ambiguity over mile length resolved through the 1593 Act against Converting Great Houses which codified the statute mile as 5280 feet.
The international yard and pound agreement signed July 1959 defined the international yard in US and Commonwealth nations as exactly 0.9144 meters. Since one foot equals one third of a yard the international foot became exactly 0.3048 meters. This value proved two parts per million shorter than previous US definitions and 1.7 parts per million longer than prior British definitions. The agreement concluded step-by-step events initiated by British Standards Institution adoption of scientific inch measuring 25.4 millimeters in 1930.
Institute of Electrical and Electronics Engineers adopted ft as standard symbol for foot. Some cases denote foot using prime often approximated by apostrophe. Inch appears with double prime example showing 2feet 4 inches sometimes written 2′4″. Imperial units previously defined foot as one third yard realized as physical standard separate from meter. Yard standards across Commonwealth countries compared periodically during years 1947 to 1948 and again in 1957.
National Physical Laboratory determined UK primary yard standard in terms of meter during 1964 implying pre-1959 UK foot measured 0.304799 meters. United Kingdom adopted international yard through Weights and Measures Act 1963 effective the 1st of January 1964. Thoburn v Sunderland City Council case dated the 18th of February 2002 further clarified legal standing.
When international foot defined in 1959 great deal survey data already existed based on former definitions especially US and India. Small difference between survey foot and international foot undetectable on small parcel surveys becomes significant for mapping or state plane coordinate system usage. Origin of system may lie hundreds of thousands feet from point of interest. Previous definitions continued used for surveying in US and India many years denoted survey feet distinguish them from international foot.
United States defined foot as 12 inches with inch defined by Mendenhall Order 1893 via 39.37 inches equals one meter making US foot exactly 0.3048006 meters approximately. On the 31st of December 2022 National Institute of Standards Technology, National Geodetic Survey, and Department of Commerce deprecated use of US survey foot. They recommended conversion to either meter or international foot measuring 0.3048 meters.
Historic relevance persists though Federal Register notes state legislation determines conversion factor for everyday land surveying and real estate transactions. Difference two parts per million no practical significance given precision normal surveying measurements over short distances usually much less than mile. Out of 50 states and six other jurisdictions 40 legislated surveying measures should base on US survey foot. Six legislated basis on international foot while ten have not specified.
International Organization for Standardization defined intermodal containers using feet rather than meters for leading outside corner dimensions. All ISO-standard containers remain 8 feet wide today. Outer heights and lengths primarily defined in derived from feet quantities global shipping containers still counted in twenty-foot equivalent units TEUs. This system enables efficient global freight cargo shipping despite metrication trends elsewhere.
Everyday global civilian air traffic continues controlled flight levels separated thousands feet typically read out hundreds example flight level 330 means 10060 meters altitude. Measurement altitude international aviation one few areas where foot used outside English-speaking world. Foot remains legal recognized United Kingdom road distance signs must use imperial units though distances marked miles yards not feet bridge clearances given meters feet inches usage widespread British public measurement height.
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Common questions
What is the length of the long foot used at Stonehenge?
The long foot measures 12.672 inches or 0.3219 meters. Archaeologists found this unit in stone lintels and the southern circle diameter at Stonehenge.
How did Roman standards for the foot differ from Greek measurements?
The standard Roman foot measured roughly 296 millimeters while Greek feet varied between 280 and 340 millimeters. Both cultures originally divided their feet into 16 digits before Romans later subdivided them into 12 inches.
When was the international foot officially defined as 0.3048 meters?
The international yard and pound agreement signed July 1959 defined the international foot as exactly 0.3048 meters. This value proved two parts per million shorter than previous US definitions and 1.7 parts per million longer than prior British definitions.
Which countries still use survey feet instead of the international foot today?
Forty out of fifty states and six other jurisdictions have legislated that surveying measures should be based on US survey foot. The United States and India continue to use these former definitions for mapping and state plane coordinate systems despite the 1959 international definition.
What is the width of ISO-standard shipping containers in feet?
All ISO-standard containers remain 8 feet wide today. International Organization for Standardization defines intermodal container dimensions using feet rather than meters for leading outside corner measurements.