The natural draft wet cooling towers are used extensively due to its less operating and maintenance costs. It is imperative to design the geometry of these towers optimally. This leads to improvement of total cost of cooling tower for its life cycle. The present work relates to find the optimum geometry of hyperbolic natural draft wet cooling towers for power plants. The total life-cycle cost function is the sum of capital and operational cost. The Six variables i.e. diameter of tower shell at bottom, diameter of shell at top, height of the shell, height of shell at air inlet opening, height of fill, frontal area of fill have been considered to affect the total life cycle cost. In order to prevent cold inflow of air from top, the diameter of shell at top can be taken a fixed ratio of diameter of shell at air inlet opening. Frontal area of fill can also be related to area/ diameter of shell at air inlet opening. The height of fill can be found on the basis of tower height and bottom diameter of shell by neglecting the losses across fill. Thus this problem of six variables may be reduced to three variables that can be easily solved.