A triangular prism has a triangular base and top with vertical sides joining the base and top. The surface area is the areas of the base and top plus the three rectangular faces. If the length of the prism is h, and the sides of the triangle are a, b and c, the area of the rectangular sides are ah, bh and ch. The area of the base or top can be found using Heron's formula, where s=(1/2)(a+b+c) in sqrt(s(s-a)(s-b)(s-c))=A, the area. Therefore the total surface area is 2A+2hs.