The chapter “Naval Stability Calculation” explores the fundamental principles governing a ship’s equilibrium, buoyancy, and resistance to capsizing under various conditions. It begins by defining equilibrium in ship stability, where gravitational and buoyant forces are balanced, and introduces Archimedes’ Principle as the foundation for buoyancy calculations. The text details how the center of gravity (G), center of buoyancy (B), and metacenter (M) interact to determine whether a vessel is in stable, neutral, or unstable equilibrium, emphasizing the importance of metacentric height (GM) as a measure of stability. It also discusses hydrostatic pressure and its role in generating buoyant force, along with the influence of factors such as loading, damage, and free surface effect on stability. The chapter further examines transverse and longitudinal stability, providing mathematical formulations for metacentric radius, metacentric height, and center of flotation, and includes example calculations for practical understanding. Finally, it introduces the concepts of moment of inertia and the parallel axis theorem as tools for analyzing the ship’s resistance to rolling and pitching, concluding with composite examples that illustrate how geometric properties influence a vessel’s overall stability.