A square with an area of 49 square inches has a perimeter of 28 inches. According to About.com, the formula for the area of a square is length times width. Since a square has equal sides, the equivalent formula is a side squared.
The square root of 49, or 7 inches, is then the length of one side. The formula for the perimeter of a square is the sum of all sides. Since all sides are 7 inches, the perimeter is 7 + 7 + 7 + 7, or 28 inches. The area of the square is reported in square inches because inches are multiplied by inches to yield square inches.