⛵ Hull Speed Calculator
Calculate the theoretical maximum hull speed of a displacement-hull boat based on its waterline length.
What is hull speed?
Hull speed is the theoretical maximum speed a traditional displacement-hull boat (one that pushes through the water rather than planing on top of it) can efficiently reach. Beyond this speed, the boat’s own bow and stern waves interfere so much that it takes drastically more power to go any faster.
The formula
Hull speed is calculated from the boat’s waterline length using the classic naval architecture formula: Hull Speed (knots) = 1.34 × √LWL (feet). This comes from the physics of the wave a hull generates: a longer waterline produces a longer wavelength wave, which travels faster, letting a longer boat achieve a higher hull speed before hitting this wave-making limit.
This rule applies to traditional displacement hulls — planing hulls (speedboats, many powerboats) and hulls designed to surf their own bow wave can exceed this theoretical limit by rising up and skimming across the water instead of pushing through it.
For general boat design and reference purposes only.