Boat Planing Horsepower & Speed Calculator
Calculate minimum engine horsepower (HP) required to get a powerboat onto plane, predict top speed using naval architect George Crouch’s formula, and compute cruising fuel economy.
Vessel Displacement & Power
lbs
Hull dry weight + motor + fuel + gear + passengers.
HP
Total prop shaft horsepower.
ft
Hydrodynamic Planing Status
FULLY PLANING HULL
Estimated Top Speed (Crouch)
40.5 MPH
35.2 Knots top speed
Minimum Planing Horsepower
117 HP
Required to climb bow wave over hump
Power-to-Weight Ratio
23.3 lbs / HP
Under 30 lbs/HP benchmark
Displacement Hull Speed (Hump)
5.9 Knots
1.34 × √LWL pre-planing barrier
Cruising & Fuel Efficiency Estimate
Economical Cruising Speed (~75% RPM):
30.4 MPH (26.4 Knots)
Estimated WOT Fuel Burn:
15.0 GPH (gallons per hour)
Cruise Fuel Economy:
~3.0 to 3.4 MPG
Crouch’s Naval Architecture Formula
Marine Engineering
Top Speed (MPH) = C ÷ sqrt(Weight / HP). Minimum planing threshold occurs at 25–30 lbs per horsepower. When power-to-weight exceeds 40 lbs/HP, boats struggle to climb over their bow displacement wave hump and remain trapped in high-drag semi-displacement mode.