This paper describes the influence of shipform characteristics on resistance increase and speed loss in wind and waves. Resistance increase and speed loss are estimated by calculation. The estimations are carried out for 4 kinds of ships, which are general cargo ships, bulk carriers, pure car carriers and container ships. The particulars of these ships are standardized by auther's former research based on the data of many actual ships. The relations between ship's dimensions and enlargement of resistance increase on each kind of ships are analyzed. And the estimated results of resistance increase of the standardized ships are showed in the form of residual resistance. Furthermore, ship's performance and required power in still water of these standardized ships are supposed by using the latest data of actual ships. Speed loss in wind and waves is predicted by using those performance data. And finally the relations between ship's dimensions and speed loss on each kind of ships are analyzed. The result of these analyses shows that huge ships with low service speed have a trend of causing a great deal of speed loss in wind and waves.