Hull speed: a theoretical speed reference
It is neither an absolute maximum speed nor a cruising-speed promise.
Conventional formula
Hull speed (kn) ≈ 1.34 × √LWL_ft ≈ 2.43 × √LWL_mIn plain language
The conventional rule relates speed to the square root of LWL. With LWL in feet, 1.34 gives knots; with metres, the equivalent coefficient is approximately 2.43.
How to interpret it
It is a reference associated with wave generation in displacement mode, not a universal physical barrier.
Why it matters
It helps put speed expectations for a conventional monohull into context.
Limitations
Hull form, planing, surfing, wind, loading and power alter behaviour. It is not a passage prediction.
In practice
Hypothetical example: a 9 m LWL gives a reference of approximately 7.29 knots.
Sources & reading
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