GM from Rolling Period

Estimate effective GM from an observed natural rolling period using the Weiss/IMO formula - no inclining test required.

StabilityGM

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

GM = \frac{4 \pi^2 (C \cdot B)^2}{g \cdot T^2}

Symbol	Meaning	Unit
$B$	Ship beam at waterline	m
$T$	Natural rolling period	s
$C$	Empirical roll factor (≈0.373)
$g$	Gravitational acceleration	m/s²
$GM$	Metacentric height	m

Source: IMO Res A.749(18) - IS Code Part B §3.2; Derrett & Barrass Ch.16

Estimate effective GM from an observed natural rolling period using the Weiss/IMO formula - no inclining test required.