Surface area is the total area on the surface of a three-dimensional shape. The main formula you can use is SA = 2lw + 2lh + 2hw. This means that you would first multiply the length by the width and multiply that product by 2, multiply the length and the height and multiply that product by 2, and lastly multiple the width and the height and multiply that product by 2. After you multiply what you need to multiply, you add all of your products together, thus resulting in the surface area of the figure.