Rudder Area Calculator
Calculate minimum rudder area and dimensions from lateral plane area and desired percentage.
Inputs
ft²
%
Results
Rudder Area
4.8 ft²
≈ 7 sheets of paper
Rudder Area (metric)0.45 m²
Rudder Span3.1 ft
Rudder Chord1.55 ft
How to Use This Calculator
- Enter the lateral plane area (LPA) of the hull in square feet — typically from design drawings.
- Set the rudder area percentage (typically 1.5-2.5% of LPA) and desired aspect ratio.
- Review the recommended rudder area in sq ft and m².
- Check the rudder span and chord dimensions to guide fabrication.
- Increase the percentage if greater maneuverability is needed for tight-harbor operations.
How the result changes with Lateral Plane Area
| Lateral Plane Area | Rudder Area |
|---|---|
| 5,005 | 200.2 ft² |
| 17,503 | 700.12 ft² |
| 32,502 | 1,300.08 ft² |
| 45,001 | 1,800.04 ft² |
What each input means
- Lateral Plane Area
- Total underwater profile area of the hull viewed from the side.
- Rudder Area Percentage
- Typical range: 2-5% for sailboats, 3-5% for powerboats, up to 8% for tugboats.
- Rudder Aspect Ratio
- Span²/Area. Higher aspect ratios (2-3) are more efficient. Spade rudders typically 1.5-3.
How this is calculated
Worked example, using the default values
- Identify Input ParametersLateral Plane Area = 120, Rudder Area Percentage = 4, Rudder Aspect Ratio = 2 = 3 input(s) provided
- Calculate Rudder AreaRudder Area4.8 = 4.8
- Calculate Rudder AreaRudder Area0.4459 = 0.4459
- Calculate Rudder SpanRudder Span3.1 = 3.1
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