Hull Speed Calculator
Calculate theoretical maximum speed and speed/length ratio for displacement hulls
Results
Theoretical Hull Speed
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LWL (feet)
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Speed/Length Ratio at Hull Speed
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Actual Speed S/L Ratio
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% of Hull Speed
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Speed/Length Ratio Guide
| S/L Ratio | Description | Power Requirement |
|---|---|---|
| 0.0 - 0.9 | Easy cruising | Low - moderate |
| 1.0 - 1.1 | Efficient cruising | Moderate |
| 1.2 - 1.34 | Near hull speed | High |
| 1.34 | Hull speed | Maximum efficient |
| > 1.34 | Semi-planing | Very high |
About Hull Speed
Hull speed is the theoretical maximum speed at which a displacement vessel can travel efficiently. It's determined by the wavelength created by the bow wave.
Formula: Hull Speed (knots) = 1.34 × √LWL (feet)
The constant 1.34 comes from the relationship between wave speed and wavelength. When a boat reaches hull speed, its bow wave wavelength equals the waterline length.
Note: Light displacement vessels, planing hulls, and multihulls can exceed theoretical hull speed. This calculation applies primarily to heavy displacement monohulls.