Hull roughness due to corrosions of outer hull and had applications on outer hull paints was analyzed theoretically. It's value which was gainable practically, was studied, and estimated power penalty formular correspon-ding to that value were reviewed. Local roughness penalty and roughness texture penalty that paint manahers in ship yard can easily were compared and studied by dotting actual ships in the issued curves. Losses and benifits of hull roughness & the specification choise of A/F paint which managers of ship maintenance were much interested in have been calculated through actual ships. The paper is illustrating that how much the specification choise and managing of A/F paint have effects on fuel consumption of ship in program. It is urgently required that recent developed antifouling paints of new A/F generation should be adopted to new ship building by big shipping companies in view of the environmental protection and the economical maintenance of ships.