The perimeter, P, is: Example. Find the perimeter of this rectangle: The area is measurement of the surface of a shape. To find the area of a rectangle or a square you need to multiply the length and the width of a rectangle or a square. Area, A, is x times y.Example. Find the area of this square. There are different units for perimeter and area The perimeter has the same units as the length of the sides of rectangle or square whereas the area's unit is squared. Video lesson: Calculate the perimeter and the area in feet. 1  Pre-Algebra. 2  Algebra 1.3  Algebra 2. 4  Geometry.rea, A, is x times y. Example. Find the area of this square. There are different units for perimeter and area The perimeter has the same units as the length of the sides of rectangle or square whereas the area's unit is squared. Video lesson: Calculate the perimeter and the area in feet. 1  Pre-Algebra. 2  Algebra 1.