The formula that is used to calculate the surface area of a triangular prism is, Surface area = (Perimeter of the base × Length of the prism) + (2 × Base Area) = (S 1 + S 2 + S 3 )L + bh ; where 'b' is the bottom edge of the base triangle, 'h' is the height of the base triangle, L is the length of the prism and S 1 , S 2 and S 3 ...