A galleryless steel piston for an internal combustion engine is provided. The piston has a monolithic piston body including an upper wall forming an upper combustion surface with first and second portions. The first portion extends annularly along an outer periphery of the upper wall and the second portion defines a combustion bowl. The piston further includes undercrown surface located directly opposite the combustion bowl with an exposed 2-dimensional surface area allowing for contact of cooling oil. The exposed 2-dimensional surface area ranges from 25 to 60 percent of a cross-sectional area defined by a maximum outer diameter of the piston body. To further enhance cooling, a portion of the undercrown surface is concave or convex, such that oil is channeled during reciprocation of the piston from one side to the opposite side of the piston.