How The Calculation Is Done

Core Principles

This calculator implements naval architecture formulas based on Archimedes’ Principle and standard marine engineering calculations for vessel displacement and buoyancy.

Calculation Formulas

Displacement Volume Calculation

Displaced volume is calculated using the main hull dimensions multiplied by a block coefficient that accounts for the actual shape of the hull rather than assuming a perfect rectangular block.

Volume = Waterline Length × Beam × Draft × Block Coefficient

Where:

• Waterline Length (LWL): Length of the vessel at the waterline
• Beam: Maximum width of the hull at the waterline
• Draft: Vertical distance from waterline to lowest point of the hull
• Block Coefficient: Ratio of actual displaced volume to rectangular block volume of the same dimensions

Block coefficient is adjusted for both vessel type and hull form to provide accurate real-world values.

Displacement Weight Calculation

Once displaced volume is known, total displacement weight is calculated by multiplying volume by the density of the water the vessel is floating in.

Displacement = Volume × Water Density

Standard water density values:

Volume From Known Displacement

When displacement weight is already known, the calculator works backwards to find the actual volume of water that is being displaced.

Volume = Displacement ÷ Water Density

Coefficients Reference

Vessel Type Block Coefficients

Each vessel type has characteristic hydrodynamic coefficients based on standard hull designs:

Hull Form Adjustments

Additional adjustments are applied based on the specific hull form design:

Additional Calculations

Wetted Surface Area

Total hull surface area that is in contact with water:

Wetted Surface = LWL × (2 × Draft + Beam) × √(Block Coefficient) × 0.65

Reserve Buoyancy

Percentage of additional buoyancy available above the loaded waterline:

Reserve Buoyancy % = (Total Hull Volume - Displaced Volume) ÷ Displaced Volume × 100

Buoyant Force

According to Archimedes’ Principle, the upward buoyant force acting on a vessel is exactly equal to the weight of the water that it displaces:

Buoyant Force = Displaced Weight

Unit Conversions

All calculations are normalized to imperial units internally before processing. Input values are automatically converted from metric units as required.

Calculation Flow

1. Input Validation: All dimensions and values are checked for positive numeric values
2. Unit Conversion: All inputs converted to consistent base units
3. Coefficient Selection: Appropriate coefficients are selected based on vessel type and hull form
4. Volume Calculation: Displaced volume calculated from dimensions or known displacement
5. Displacement Calculation: Weight displacement calculated using water density
6. Derived Metrics: Wetted surface, reserve buoyancy and other values computed
7. Results Formatting: Values are formatted and returned for display

Accuracy Notes

• Calculations are estimates based on standard naval architecture coefficients
• Actual vessel displacement may vary due to hull shape irregularities
• Results are suitable for planning and estimation purposes only
• For critical applications always use official vessel stability documentation