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Boat Speed Calculator

Estimate boat top speed using Crouch's Formula.

Total Weight (lbs)

Include engine, fuel, passengers, and gear.

Total Horsepower (HP)

Hull Type

Enter weight and horsepower to see the estimated speed.

Crouch's Formula

Uses the formula: Speed = C / √(Weight/HP). 'C' is a constant based on the hull type and efficiency.

Weight Factor

Total weight significantly impacts speed. Ensure you include fuel (approx 6 lbs/gallon), gear, and passengers.

Hull Types

Different hulls have different 'C' constants. Racing hulls (Hydroplanes) are more efficient than heavy Cruisers.

Features

Speed Estimate

Calculate theoretical top speed in MPH, Knots, and KPH.

Crouch's Formula

Uses industry standard formula for hull efficiency.

Hull Types

Presets for Runabouts, Cruisers, Hydroplanes, and more.

About Boat Speed Calculator

The Boat Speed Calculator helps boat owners and enthusiasts estimate the potential top speed of a vessel based on its weight and horsepower. It uses Crouch's Formula, a widely accepted method for predicting boat performance.

How to Use Boat Speed Calculator

1
Enter Weight
Input the total weight of the boat including engine, fuel, and gear.
2
Enter Horsepower
Input the total shaft horsepower of the engine(s).
3
Select Hull Type
Choose the hull type that best matches your boat to set the efficiency constant.
4
View Speed
See the estimated top speed in MPH, Knots, and km/h.

Frequently Asked Questions

Crouch's Formula is Speed = C / sqrt(Weight / Horsepower), where C is a constant representing hull efficiency. It is the industry standard for estimating marine performance.

The estimate is purely theoretical. Real-world factors like propeller efficiency, water conditions, wind, and weight distribution will affect the actual top speed.

The C-Constant represents how efficiently a hull moves through water. Planning hulls have higher constants (150+), while heavy displacement hulls have lower ones (150 or less).

Yes, the propeller's job is to convert engine power into thrust. If the pitch is too low, the engine will hit the rev limiter; if too high, the engine won't reach its power band.

Common reasons include bottom fouling (algae/barnacles), excess gear weight, poor engine tune, or using an incorrect C-Constant for your hull type.

Proper 'trim' is essential. If the bow is too heavy (plowing), drag increases. If the stern is too heavy (porpoising), the boat becomes unstable and loses speed.