A square inch is a unit

Units of measurement

A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...

 of area

Area

Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...

, equal to the area of a square

Square (geometry)

In geometry, a square is a regular quadrilateral. This means that it has four equal sides and four equal angles...

 with sides of one inch

Inch

An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

. 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

or in some cases "^2

The square inch is a common unit of measurement in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 and the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

.

Equivalence with other units of area

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

Repeating decimal

In arithmetic, a decimal representation of a real number is called a repeating decimal if at some point it becomes periodic, that is, if there is some finite sequence of digits that is repeated indefinitely...

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

Square yard

The square yard is an imperial/US customary unit of area, formerly used in most of the English-speaking world but now generally replaced by the square metre outside of the U.S., Canada and the U.K. It is defined as the area of a square with sides of one yard in length...

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

Square metre

The square metre or square meter is the SI derived unit of area, with symbol m2 . It is defined as the area of a square whose sides measure exactly one metre...

s (1 square metre is equal to square inches)