Rectangles Tutorial for SAT/GRE Test Preparation
Squares are called squares because they have equal length sides.The perimeter of the square is the sum of the lengths of the sides. And since all the sides are equal, this is just four times the length of one side.
Perimeter of a square = s + s + s + s = 4s The area of a square is the length of one side multiplied by the length of another. But since these are the same, it is also s². Area of a square = s × s = s² (Now do you see why they are called squares?) 

Now imagine the square having a third dimension, also of size s. The volume would be the width × length × height. And since all three dimensions are the same size we have:Volume = s × s × s = s³  
Not all rectangles have four equal sides, however. All squares are rectangles, in other words, but not all rectangles are squares. To calculate the perimeter of a rectangle that is not a square, simply add the four sides:Perimeter = w + l + w + l = 2w + 2l The area is the product of the length and the width.
Area = l × w 

Now, imagine a rectangular shape, and then add a third dimension. This would be called a prism. The volume would be the product of all three dimensions.Volume = Length × Width × Height = l × w × h 
As always, volume is measured in cubic distance units.