The article presents the methodology of calculation of principal parameters of ship’s hull dimensions, called „significant ships list”, at preliminary stage of design process. Knowledge collected in the database is related to new buildings classified according to type, displacement, or DWT, shipping class, maximum speed etc. Are analysed dimensional constraints due of Froude Number, ships dimensional coefficients block and weigh coefficient, relations of main dimensions such as L/B, B/T, L/H, B/H etc. . Those parameters coming out from ship-owners requirements like type of ship, load capacity, type of cargo, shipping zone, speed and some more. Very helpful tool for such analysis is list of significant ships created for specified types of ships. Mentioned lists are very effective under conditions that cover broad-spectrum new buildings and data included are credible. Uncritical taking values included in significant ships list can lead to critical errors in selection of main dimensions of a ship or its propulsion powering. For that reasons, basing on analysis, as main criteria of similarity of ship’s hull were assumed mass coefficient, block coefficient and Froude Number . That procedure has significant impact at proper estimation of propulsion power. Another reliable parameter of evaluation of power seems to be relation between power and load capacity Ne/D.