A prism is a three-dimensional shape with two parallel, congruent bases.[1] In a triangular prism, the bases are triangles. A triangular prism also has three lateral sides. To find the surface area of triangular prism, you first need to find the area of the lateral sides, then you need to find the area of the bases. Finally, you need to add these two areas together to find the total surface area. These steps are represented by the formula Surface area = L + 2B , where L equals the lateral area of the prism and B equals the area of one base