Hull speed is a rule‑of‑thumb that estimates the maximum speed a displacement‑type vessel can achieve before it must climb its own bow wave. Below this speed the hull moves efficiently through the water, but as the speed approaches hull speed the wave resistance grows dramatically.
The phenomenon arises because a displacement hull creates a transverse wave system whose wavelength is proportional to the vessel’s waterline length. When the wavelength matches the waterline, the hull sits in a trough between the bow and stern waves, limiting further acceleration without planing.
For practical calculations the empirical formula Vmax = 1.34 √LWL (with V in knots and LWL in feet) provides a quick estimate of this speed limit. By inserting the waterline length of a vessel, designers can gauge whether a proposed hull form will meet performance expectations.
L_{WL} = waterline length (ft)
What is hull speed?
How do I calculate my boat's hull speed?
Why does hull speed matter for a boat?
Can I exceed my boat's hull speed?
What factors can affect a boat's actual top speed?
Is there a way to improve my boat's performance at speeds above hull speed?
How does hull speed relate to displacement and planing boats?
Results are for informational purposes only and do not constitute professional advice.