A reinforced concrete slab is supported directly by concrete columns without the use of beams. Flat slabs are highly versatile elements widely used in construction, providing minimum depth, fast construction and allowing flexible column grids. In this work, an attempt is made for optimum design of reinforced concrete flat slab with drop panel is according to the IS code method. The objective function is the total cost of the structure including the cost of the slab, drop and columns. The cost of each structural element covers that of materials (steel, concrete). In this work, a program in MATLAB was written for a flat slab with a drop by direct design method. Using this MATLAB program parameter optimization process is done for different span in both the directions. From this optimization, it is found that the cost of a flat slab decreases as the number of span increases by keeping the total length of the slab as constant.