Nets and surface area

A cuboid has six rectangular faces, in three equal pairs: top and bottom, front and back, left and right. If we unfold it we get a net, a flat shape with all six faces. The surface area is the sum of the areas of the six faces, measured in square units (cm² or m²). For a cuboid with length l, width w and height h, the top and bottom are l × w each, the front and back are l × h each, and the two sides are w × h each. So surface area = 2 × (l × w + l × h + w × h). In a drawing you see only three faces, so remember the three hidden faces that are equal to them.