A square inch (plural: square inches) is a

unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action, a discrete piece of action (or beat) in a theatrical presentation Music * ''Unit'' (a ...

area Area is the quantity that expresses the extent of a region on the plane or on a curved 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 op ...

, equal to the area of a

square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length a ...

with sides of one

inch Measuring tape with inches The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelfth ...

. 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 (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

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 Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and ...

. A common unit of pressure,

pound per square inch The pound per square inch or, more accurately, pound-force per square inch (symbol: lbf/in2; abbreviation: psi) is a unit of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force of one pound-force applied ...

(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 decimal representation of a number whose digits are periodic (repeating its values at regular intervals) and the infinitely repeated portion is not zero. It can be shown that a number is rational i ...

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

square yard The square yard ( Northern India: gaj, Pakistan: gaz) is an imperial unit and U.S. customary unit of area. It is in widespread use in most of the English-speaking world, particularly the United States, United Kingdom, Canada, Pakistan and Indi ...

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

square centimetre 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 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) {{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