Boat Speed Calculator
Estimate the maximum theoretical speed of a displacement hull boat based on its waterline length.
This is the length of the boat at the point where it sits in the water, not the overall length.
What is Hull Speed?
For displacement boats (like most sailboats), the maximum efficient speed is limited by the wave system the boat creates. As the boat moves, it creates a bow wave. At "hull speed," the boat is trapped between its bow wave and its stern wave, effectively trying to climb uphill.
The Formula
The standard formula is:
Speed (knots) = 1.34 × √LWL (feet)
This does not apply to planing hulls (like speedboats), which can rise up and skim over the water, exceeding this limit.