Planing Hull Speed Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Planing Hull Speed Calculator
How fast will a planing hull boat realistically go? This calculator applies Crouch's formula, a long-used naval architecture rule of thumb based on power-to-weight ratio.
Speed (mph) ≈ C × √(HP / (Weight/1000))
Example
200 horsepower, 4,000 lb boat weight (including fuel, gear, passengers):
Power-to-Weight = 50 HP per 1,000 lbs → Estimated Top Speed ≈ 44.1 mph
Why This Is a Rough Estimate
Crouch's formula uses an empirical constant that varies by hull type - light racing hulls, average recreational runabouts, and heavy cruisers each use a meaningfully different constant, since hull shape efficiency varies enormously across these categories. This calculator assumes a typical recreational planing hull runabout, not a precise prediction for any specific hull design.
Other Factors That Matter
Actual top speed also depends heavily on propeller selection (wrong pitch or diameter can leave significant speed on the table), hull condition (marine growth or damage reduces speed), and water conditions (calm water versus chop) - this calculator gives a useful ballpark starting estimate, not a guaranteed number.