A square inch (plural: square inches) is a unit of

area Area is the measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...

, equal to the area of a

square In geometry, a square is a regular polygon, regular quadrilateral. It has four straight sides of equal length and four equal angles. Squares are special cases of rectangles, which have four equal angles, and of rhombuses, which have four equal si ...

with sides of one

inch The inch (symbol: in or prime (symbol), ) is a Units of measurement, unit of length in the imperial units, British Imperial and the United States customary units, United States customary System of measurement, systems of measurement. It is eq ...

. The following symbols are used to denote square inches: *square in *sq inches, sq inch, sq in *inches/-2, inch/-2, in/-2 *inches^2, inch^2, in^2 *inches², inch², in² (also denoted by "^²) *historic engineering drawings ^□″ (number with a square & a double apostrophe, both as an exponent) The square inch is a common unit of measurement in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

. A common unit of pressure, pound per square inch (psi) is derived from this unit of area.

Equivalence with other units of area

1 square inch (assuming an international inch) is equal to: (the overbars indicate

repeating decimal A repeating decimal or recurring decimal is a decimal representation of a number whose digits are eventually periodic (that is, after some place, the same sequence of digits is repeated forever); if this sequence consists only of zeros (that i ...

s) * square feet (1 square foot is equal to 144 square inches) *

square yard The square yard (Indian English, Northern India: guz, gaj, Pakistani English, Pakistan: gaz) is an imperial unit and U.S. customary unit of area. It is in widespread use in most of the English language, English-speaking world, particularly the U ...

s (1 square yard is equal to 1,296 square inches) * square centimetres (1 square centimetre is equal to square inches) *

square metre The square metre ( international spelling as used by the International Bureau of Weights and Measures) or square meter ( American spelling) is the unit of area in the International System of Units (SI) with symbol m2. It is the area of a square ...

s (1 square metre is equal to square inches)

References

{{DEFAULTSORT:Square Inch Units of area Imperial units Customary units of measurement in the United States ja:インチ#平方インチ