Boat Speed Calculator
Estimate boat speed from horsepower and displacement, or solve for the horsepower needed to reach a target speed.
The calculator follows the classic Crouch-style relationship: speed is proportional to the square root of horsepower divided by displacement.
Boat Speed Result
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Run the calculation to see the estimated speed or horsepower.
Quick Answer
Boat speed rises with horsepower and falls as displacement increases, so a lighter hull or more power generally means a faster boat.
How to Use It
- Choose whether you want speed or horsepower.
- Enter the horsepower, target speed, and displacement.
- Pick a hull type and coefficient.
- Click Calculate.
Formula
Speed = coefficient × sqrt(horsepower / displacement)
Horsepower = displacement × (speed / coefficient)²
Worked Examples
Example 1: 200 hp, 4,500 lb displacement, and a coefficient of 180 gives about 38 mph.
Example 2: To reach 30 mph with the same coefficient and displacement, you need about 125 hp.
Example 3: A heavier cruiser needs more power than a lighter sport boat to reach the same speed.
How to Interpret the Result
| Output | Meaning |
|---|---|
| Speed | Estimated boat speed in miles per hour. |
| Horsepower | Approximate power needed to reach the target speed. |
| Coefficient | A hull-factor constant that changes with boat style. |
Frequently Asked Questions
Related Calculators
References
- OmniCalculator reference page
- The reference page uses a speed-to-power relation based on horsepower, displacement, and hull coefficient.
- Last reviewed: March 2026.