稳心是判断一个浮水面的物体的稳定度的重要指标，用以判断物体是否可以稳定的浮在水面上而不致于翻覆。稳心高度是稳心到浮体的重心的距离。 一个飘浮的对象通常会受到两个力，浮力及重力；；重力的作用点为物体的质量中心(G)，浮力的作用点为浮力中心(B)。注意浮力中心即为物体沉默部份的体积中心。当物体转动时，质量中心G的位置永远不变，但是浮力的作用位置B会改变。稳心的求法，一先找出物体的中线，也就是若物体稳定平衡在水面上时，链接GB的线；中线与过浮力中心的铅直线的交点即为稳心。

注意当浮体的转动角度很小的时候，稳心的位置固定，只有浮力中心的位置会改变；但当转动角度过大时，稳心跟浮力中心的位置都会有变化。

The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stability against overturning. The metacentric height also influences the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers. Hence, a sufficiently high but not excessively high metacentric height is considered ideal for passenger ships.