Foot (ft)

US & ImperialCurrent unit

12 inches. Defined as exactly 0.3048 meters. Still the standard unit for height, altitude in aviation and room dimensions in the US and UK.

1 foot = 0.3048 meters (exactly).

About the foot

Human anatomy supplied the idea: an adult foot is roughly 15 percent of body height. Ancient cultures turned that into standards, but not the same one. The Greek pous was about 302 mm, the standard Roman pes about 295.7 mm, and a Harappan foot of about 335 mm has been reported from the Indus Valley. Historically, a foot fell somewhere between about 250 and 335 mm. Charlemagne tried to standardize units around 790 with little lasting success, and in 1593 English law fixed the statute mile at 5,280 feet.

The modern foot dates from the 1959 International Yard and Pound Agreement, which defined the yard as exactly 0.9144 meter and so the foot as exactly 0.3048 meter; the UK adopted it on 1 January 1964. The US survey foot, defined in 1893 as 1200/3937 meter, was deprecated on 31 December 2022. Feet remain in everyday use for height and rooms in the US, and ISO shipping containers are defined in them. Aviation altitudes use them too: flight level 330 means 33,000 feet.

Sources: Wikipedia: Foot (unit); Wikipedia: Mile; NIST Guide to the SI, Appendix B.8: conversion factors

Foot conversion chart

1 foot expressed in every other length unit:

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