A square inch (plural: square inches) is a unit of area, equal to the area of a square with sides of one inch. 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)