Boat performance

Hull speed

The practical speed limit of a displacement hull, from its waterline length.

Inputs

Waterline length (LWL)

Current speed (knots, optional)

Result

Hull speed—

Hull speed (mph / km/h)—

Speed/length ratio at current speed—

Regime—

Hull speed = 1.34 × √LWL (feet) knots, equivalently 2.43 × √LWL (metres). It is the speed at which the boat's wave length equals its waterline length. Light, planing, and multihull designs can exceed it; heavy displacement boats find it very costly to.