A drain pan assembly for receiving liquids from air conditioners, refrigerators, and freezers comprising a blank having peripheral edges, base forming fold lines, and corner piece forming fold lines, wherein at least two corner piece forming fold lines and a portion of the peripheral edges, form each corner piece. The corner piece further comprises a diagonal corner fold line. Folding each corner piece along each diagonal corner fold line forms corner flaps. Each corner flap is bent about each of the corner piece forming fold lines to dispose the corner piece forming fold lines adjacent to each other and the diagonal corner fold lines adjacent to a surface of each peripheral wall.