foot

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A measure of length in the English-speaking world; since the 12th century, the foot has been legally defined as one-third of a yard. Since 1959, one foot = 0.3048 meter exactly; see yard and below.

The foot is only roughly the size of a human foot. The median foot of American males (as many smaller as bigger) is 10.4 inches long, and the female median is an inch smaller. Even 17-year old U.S. Army trainees have a median foot length of only 10.6″, and 95% of them have feet smaller than 11.2″.

The most recent change in the length of the foot was the result of an agreement among the English-speaking countries to eliminate discrepancies between their customary measures. The United States implemented the agreement by an announcement in the Federal Register on July 1, 1959 (“Refinement of Values for the Yard and the Pound”), and since then in the United States the foot has been the international foot = 0.3048 meter exactly. Since the United States is now almost the only country still using the foot, the name has become something of a joke.

U.S. Survey foot

The United States uses a different foot for one activity. When the United States adopted the international yard in 1959, the U.S. Coast and Geodetic Survey, mappers of the nation, objected that converting all their geodetic data to international feet would be a horrendous undertaking. They were authorized to continue to use the previous definition of the foot, that of the Mendenhall order (U.S. Coast and Geodetic Survey Bulletin 26, April 5, 1893), one foot = ¹²⁰⁰/₃₉₃₇ meter.

This foot is now known as the U.S. Survey foot, = 1.000 002 international feet, and is used only for land measurements.