Square inch

For other uses, see Square (disambiguation).

A square inch (plural: square inches) is a unit of area, equal to the area of a square with sides of one inch. The square inch is a common unit of measurement in the United States and the United Kingdom.^[1] Pounds per square inch (psi), a unit of pressure, are derived from this unit of area.^[2]

square inch
Unit system	Imperial, United States customary units
Unit of	area
Symbol	in2, sq in
Conversions
1 in2 in ...	... is equal to ...
Imperial/US	⁠1/144⁠ sq ft ⁠1/1296⁠ sq yd
SI units	6.4516 cm2 6.4516×10−4 m2

Representations

The following symbols are used to denote square inches:^[1][2][3]

• 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 usage ^□″ (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 decimals):^[2][4][5]

• 0.006 94 square feet (1 square foot is equal to 144 square inches)
• 0.000 771 604 9382 square yards (1 square yard is equal to 1,296 square inches)
• 6.4516 square centimetres (1 square centimetre is equal to 0.155 000 310... square inches)
• 0.000 645 16 square metres (1 square metre is equal to 1,550.003 100... square inches)
• ⁠π/4⁠ circular inches (1 circular inch is equal to ⁠4/π⁠ square inches)