In the present research, a comprehensive analytical framework is proposed for optimal sizing of louvered fin flat tube car radiators. In order to perform optimal sizing, eleven geometric variables, which are all geometric parameters of the radiator, were selected as the design parameters. These variables include large and small diameters of tubes, length and wall thickness of tubes, fins’ pitch, louvers’ pitch on each fin, length of the fin, louver length and height, fin thickness, number of fins and louver angle on fins. The effects of all of these parameters on the cooling capacity and total weight of the radiator are investigated in the form of single objective optimization problems in which cooling capacity should be maximized and total weight of the radiator should be minimized. Using the proposed framework, the cooling capacity of the radiator has increased by about 8.8% compared to the base design. It is shown that some geometric parameters have the opposite effect on objective functions. Therefore, an analytical multi-objective optimization procedure is proposed to satisfy both of the goals, simultaneously. The values of the geometric parameters determined in this paper are more practical in terms of manufacturing than the values suggested in the base design.