Input Data
Example Data Table
| Case | Displacement Volume (m³) | I (m⁴) | KB (m) | KG (m) | BM (m) | GM (m) |
|---|---|---|---|---|---|---|
| Harbor Barge | 850 | 420 | 2.40 | 3.10 | 0.4941 | -0.2059 |
| Patrol Craft | 120 | 92 | 1.10 | 1.55 | 0.7667 | 0.3167 |
| Service Pontoon | 300 | 210 | 1.55 | 1.90 | 0.7000 | 0.3500 |
Formula Used
The calculator follows the classic initial stability method for floating bodies.
BM = I / ∇ GM = KB + BM - KG GZ ≈ GM × sin(heel angle) Righting Moment = Displacement Weight × GZHere, I is the second moment of the waterplane area, ∇ is displacement volume, KB is the center of buoyancy above keel, and KG is the center of gravity above keel.
How to Use This Calculator
- Enter the vessel or floating body name for record tracking.
- Input displacement volume in cubic meters.
- Enter the waterplane second moment of area in fourth-power meters.
- Provide KB and KG values from the same vertical datum.
- Set the fluid density for seawater, freshwater, or another fluid.
- Enter a small heel angle to estimate the righting arm.
- Click the calculation button to show results above the form.
- Use the export buttons to save the result summary as CSV or PDF.
Engineering Notes
Positive GM indicates initial stability. Negative GM suggests instability.
The righting arm equation used here is accurate for small heel angles. Larger heel studies need full cross-curve or hydrostatic analysis.
This tool supports early design reviews, educational checks, and load-change screening for marine platforms, barges, pontoons, and similar floating structures.