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Calcimator

Stability GZ Curve Calculator

Calculate the righting arm (GZ) curve from hull geometry and loading to assess vessel stability.

Inputs

ft
ft
LT
ft
ft

Results

Metacentric Height (GM)

1.55 ft

≈ 5 credit cards

Maximum GZ

4.46 ft

≈ 9 smartphones

Angle of Max GZ60°
Vanishing Angle90°
KB (Center of Buoyancy)2.65 ft
BM (Metacentric Radius)2.4 ft
Max Righting Moment66.9 ft·LT
How to Use This Calculator
  1. Enter the hull beam and draft in feet, displacement in long tons, and KG (height of center of gravity).
  2. Optionally override GM if you have a measured metacentric height value.
  3. Review the metacentric height (GM) — positive GM indicates initial stability.
  4. Check maximum GZ (righting arm in feet) and the angle at which it occurs.
  5. Verify the vanishing angle exceeds 60° for adequate overall stability range.

How the result changes with Beam

BeamMetacentric Height (GM)Maximum GZ
227.22 ft16.73 ft
7183.17 ft181.17 ft
131285.17 ft618.51 ft
180539.15 ft1,168.4 ft

What each input means

Beam
Maximum beam of the vessel.
Draft
Draft at the current loading condition.
Displacement
Vessel displacement in long tons at current loading.
KG (Height of COG)
Vertical center of gravity measured from the keel. Lower values improve stability.
GM Override (optional)
If you know the exact GM, enter it here to override the calculated value. Leave at 0 to use the estimate.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Beam = 12, Draft = 5, Displacement = 15, KG (Height of COG) = 3.5 = 5 input(s) provided
  2. Calculate Metacentric Height
    1.55 = 1.55
  3. Calculate Maximum GZ
    Maximum GZ
    4.46 = 4.46
  4. Calculate Angle of Max GZ
    Angle of Max GZ
    60 = 60
  5. Calculate Vanishing Angle
    90 = 90

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