Center of gravity (G)

The center of gravity G is the mass centroid of the ship and everything aboard, the point through which the total weight acts vertically downward. Its height above keel KG is the critical input to stability: GM equals KM minus KG, so raising G lowers metacentric height and reduces the righting arm. G is found by summing weight moments (lightship plus every deadweight item) and dividing by total weight, longitudinally giving LCG and vertically VCG or KG. It is fixed by the loading, not the hull shape, and is confirmed by the inclining experiment. Free surfaces in slack tanks effectively raise G through the free-surface correction.