Metacentric Height

Metacentric height, GM, is the vertical distance between a ship’s center of gravity G and the transverse metacenter M, and it sets initial transverse stability. It is found as GM = KM minus KG, where KM comes from the ship’s hydrostatics at the draft and KG from the loading condition; slack tanks reduce it by the free surface correction. A positive GM gives a righting moment that returns the ship upright; too large a GM makes the roll stiff and uncomfortable, too small risks a list or loll. The 2008 IS Code sets minimum GM among its intact criteria.