The surface area of a rectangular prism is equal to the sum of the area of all of its faces. Said another way, the surface area is the total area covered by the 6 sides. Let's take a look at a cube. Special Case: Cube As you already know, a cube has six square faces. Suppose if each of those faces is 3 inches by 3 inches, then the area of each face is 3 x 3 = 9 square inches. And since there are six of them, the total surface area is 9 + 9 + 9 + 9 + 9 + 9 = 54 square inches. To find the surface area of any shape, you can follow the process described below: 1. Draw a net of the rectangular prism 2. Calculate the area of each face. 3. Add up the area of all the faces.