Foot (unit)
The foot is an imperial and U.S. customary unit of length equal to 12 inches or 0.3048 metres, widely used for everyday measures, aviation altitudes, and building dimensions.
Overview
The foot is a unit of length traditionally based on the size of a human foot. It is a standard measure in the Imperial and U.S. customary systems and is commonly written as ft or with a prime symbol (′). The unit remains important in several fields despite widespread adoption of the metric system in many countries. For a general definition see unit, and for its relation to length concepts consult measurement references.
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Definition and characteristics
One foot equals 12 inches and is exactly 0.3048 metres (30.48 centimetres). The standard abbreviation is ft (or ft.) and a prime mark (′) is commonly used in notations such as 6′ 2″ for six feet two inches. The inch is indicated by a double prime (″). The foot is part of the broader family of Imperial and U.S. customary units; more on those systems appears under Imperial and customary units.
History and standardization
Historically, many cultures had their own versions of a "foot" based on local standards or anatomy. Lengths varied from place to place and over time. In the 19th and 20th centuries nations moved toward standardized definitions. The modern value (0.3048 m) was internationally agreed upon during mid-20th century standardization efforts, which linked the foot to the metre for precise scientific and commercial use.
Uses and examples
The foot remains in everyday use in the United States for most distance and height measurements, in some aspects of construction and carpentry, and as the usual unit for human height. Aviation worldwide uses feet for altitude. Typical examples include room dimensions given in feet and inches, clearances and vehicle heights shown in feet, and athletes' heights listed in feet and inches. For the inch relationship see inches and for metric equivalence see centimetres.
Variations and notable facts
- Notation: feet and inches are often written together (e.g., 5′9″).
- Pluralization: the singular form as a unit is "foot"; the common plural is "feet."
- Historical variants: ancient Roman and other regional feet differed in length; these are of interest to historians and archaeologists.
- Clarification: the common measurement term derives from the body part; see general background on the anatomical term at foot.
- Related topics and deeper technical discussions can be found via general references to measurement systems at abbreviations and symbols and survey or mapping resources at standards.
Questions and answers
Q: What is a foot?
A: A foot is a unit of measurement for length.
Q: What system of units is the foot a part of?
A: The foot is part of both the Imperial units and U.S. customary units.
Q: How is the unit "foot" abbreviated?
A: The unit "foot" is abbreviated as "ft" or "ft.", or by a prime symbol ( ′ ).
Q: How many inches are in a foot?
A: There are 12 inches in a foot.
Q: What is the metric equivalent of a foot?
A: The metric equivalent of a foot is 30.48 centimetres.
Q: Why is it called a foot?
A: It is called a foot because it was originally based on the length of a foot.
Q: Is the foot used in other countries besides the United States?
A: The foot is used in some other countries besides the United States, but it is not a widely used unit of measurement globally.
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Author
AlegsaOnline.com Foot (unit) Leandro Alegsa
URL: https://en.alegsaonline.com/art/35486