The size of ships is increasing rapidly, and over 400 m length overall mega-sized container ships are predicted to appear in the near future. Consequently, studies on large container ships have been conducted; however, based on the 30,000-TEU (twenty-foot equivalent unit) class container ship’s length overall, the deviation of the predicted range showed an 83.9 m difference from 453.0 m to 536.9 m. This is because simple linear regression analysis does not consider trends according to the type of cargo or the size of the cargo. In this study, 5497 container ships up to 20 years of age with an International Maritime Organization (IMO) number registered were clustered according to the change in ship dimensions by k-means clustering algorithm. Based on the clustered data, deadweight tonnage, TEU, length overall, length between perpendiculars, breadth, and maximum draft of container ships with a coverage rate of 75% were analyzed to predict the change in the main dimensions. The results indicated that for a 30,000-TEU container ship, the predicted length overall is 428.4 m, breadth is 67.6 m, and draft is 17.0 m. This study can help minimize the social costs of designing ports in consideration of future mega-sized container ships.