Publisher Summary This chapter is designed to discuss the various aspects related to ship resistance. The resistance of ships can be predicted by several methods. One method that has stood the test of time is by William Froude in 1870. He used planks and ship models to identify and demonstrate ship resistance. Nowadays ship models may be made in wood, paraffin wax or polyurethane foam. Ship models today range from being 3 to 10 m in length. Resistance can be divided into four groups: frictional resistance, wave-making resistance, eddy-making resistance, resistance due to wind and appendages. This chapter discusses the relationship between Froude speed-length law and Froude Number. Wind and appendage allowances very much depend upon the intended route for the new vessel. It is usual practice for Naval Architects to add 10-30% onto the total resistance obtained for calm water conditions. The higher percentages appertain for vessels operating on the more heavy weather routes.