Hull Speed Calculator
Calculate theoretical hull speed from waterline length using the speed-length ratio formula.
Inputs
ft
Results
Hull Speed
7.34 knots
Hull Speed (mph)8.45 mph
Hull Speed (km/h)13.59 km/h
Froude Number0.399
How to Use This Calculator
- Enter the waterline length (LWL) in feet — measure from bow to stern at the waterline.
- Adjust the speed-length ratio if needed (default 1.34 for displacement hulls).
- Read hull speed in knots, mph, and km/h.
- Check the Froude number — values above 0.4 indicate you are pushing beyond displacement speed.
- Use this result to size engines and propellers appropriately for your hull type.
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