Hull Speed Calculator, Results


The results and the chart plot are based on an SL Ratio of 1.34 this “magical” 1.34 is just a guide as to the usual theoretical hull speed, beyond which the increasing amount of power required to push a hull past a certain speed becomes impractical. 1.34 is typical but lighter displacement boats may be allowed a higher number. Note that this number only applies to displacement hulls. Hull speed, as calculated here, is important as it is a building block to attaining figures like, what power is required and ultimately calculating what propeller may be optimum for a particular boat.

Hull Speed Chart

The chart displays speed at different percentages of theoretical hull speed. Typically you will not try to push a displacement the vessel past 100% of hull speed but I have shown the it at 125% so that in the next step it can be used to illustrate how much power is required to push the hull past this speed.


  • 1.34 * LWL^½
  • See SL Ratio for further information.