View source for Square inch

{{Short description|Unit of area}}
{{Other uses|Square (disambiguation)}}
{{Infobox unit
| name         = square inch
| image        = 
| caption      = 
| standard     = Imperial, United States customary units
| quantity     = [[area]]
| symbol       = in<sup>2</sup>
| symbol2      = sq in
| units1       = [[Imperial units|Imperial]]/[[US customary|US]]
| inunits1     = {{ubl|{{sfrac|1|144}} {{val|u=sq ft}}|{{sfrac|1|1296}} {{val|u=sq yd}}}}
| units2       = [[SI units]]
| inunits2     = {{ubl|{{val|6.4516|u=cm2}}|{{val|6.4516|e=-4|u=m2}}}}
}}

A '''square inch''' (plural: '''square inches''') is a [[Units of measurement|unit]] of [[area]], equal to the area of a [[Square (geometry)|square]] with sides of one [[inch]]. The square inch is a common unit of measurement in the [[United States]] and the [[United Kingdom]].<ref name=":0">{{Cite book |last=Cardarelli |first=François |title=Scientific Unit Conversion: A Practical Guide to Metrication |date=1997 |publisher=Springer London, Limited |others=M. J. Shields |isbn=978-1-4471-3394-0 |location=London}}</ref> [[pound per square inch|Pounds per square inch]] (psi), a unit of pressure, are derived from this unit of area.<ref name=":1">{{Cite book |last=Dresner |first=Stephen |url=http://archive.org/details/isbn_803874960 |title=Units of measurement : an encyclopaedic dictionary of units, both scientific and popular, and the quantities they measure |date=1971 |publisher=Hastings House |others=Internet Archive |isbn=978-0-8038-7496-1 |location=New York |pages=91,248}}</ref>

== Representations ==
The following symbols are used to denote square inches:<ref name=":0" /><ref name=":1" /><ref>{{Cite journal |date=1979-01-01 |title=Conversion Factors for U.S. Customary and SI (Metric) Units |url=https://doi.org/10.1093/iat/4.1.263 |journal=Insecticide and Acaricide Tests |volume=4 |issue=1 |pages=263 |doi=10.1093/iat/4.1.263 |issn=0276-3656}}</ref>
*square in
*sq inches, sq inch, sq in
*inches/-2, inch/-2, in/-2
*inches^2, inch^2, in^2
*inches<sup>2</sup>, inch<sup>2</sup>, in<sup>2</sup> (also denoted by "<sup><sup>2</sup></sup>)
*historic usage <sup>□</sup>″ (number with a square & a double apostrophe, both as an exponent)

==Equivalence with other units of area==
1 square international inch is equal to (the overbars indicate [[repeating decimal]]s):<ref name=":1" /><ref>{{US Code|15|205}}</ref><ref>{{Cite book |last=Blake |first=Alexander |url=https://books.google.com/books?id=Wp1XC3mN_2IC&dq=United+States+customary+units+handbook&pg=PA118 |title=Handbook of Mechanics, Materials, and Structures |date=1991-01-16 |publisher=John Wiley & Sons |isbn=978-0-471-86239-0 |pages=108–109 |language=en}}</ref>
* {{Nowrap|0.006 9{{Overbar|4}}}} square feet (1 square foot is equal to 144 square inches)
* {{Nowrap|0.000 7{{Overbar|71 604 9382}}}} [[square yard]]s (1 square yard is equal to 1,296 square inches)
* {{Nowrap|6.4516}} [[square centimetre]]s (1 square centimetre is equal to {{Nowrap|0.155 000 310...}} square inches)
* {{Nowrap|0.000 645 16}} [[square metre]]s (1 square metre is equal to {{Nowrap|1,550.003 100...}} square inches)
* {{Math|{{sfrac|{{pi}}|4}}}} [[Circular inch|circular inches]] (1 circular inch is equal to {{Math|{{sfrac|4|{{pi}}}}}} square inches)

==References==
{{reflist}}

{{Imperial units}}
{{United States Customary Units}}

{{DEFAULTSORT:Square Inch}}
[[Category:Units of area]]
[[Category:Imperial units]]
[[Category:Customary units of measurement in the United States]]

[[ja:インチ#平方インチ]]