Metacentric Height (GM)

Initial transverse metacentric height GM = KM − KG - the single most-cited stability criterion.

StabilityGM

Geometry

KM (transverse metacentre above keel)mFrom hydrostatic tables at current draft.KG (vertical centre of gravity above keel)mFrom loading computer after cargo + ballast + consumables.

Free-surface correction

Total free-surface correctionmSum of i·ρ / Δ across all slack tanks. Zero if all tanks are pressed up or empty.

Solid GM: 1.300m

Fluid GM: 1.220m

IS Code minimum met (≥ 0.15 m)

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

GM_\text{solid} = KM - KG, \quad GM_\text{fluid} = GM_\text{solid} - \text{FSC}

Symbol	Meaning	Unit
$KM$	Transverse metacentre above keel	m
$KG$	Vertical centre of gravity above keel	m
$FSC$	Sum of free-surface corrections	m
$GM_\text{fluid}$	Fluid metacentric height	m

Source: IMO IS Code MSC.267(85); Derrett & Barrass Ch.13

In short

Compute solid GM = KM − KG and fluid GM after free-surface correction.

Learn the theory Intact stability