How does Archimedes’ principle help naval architects predict how deeply a ship will float?

Archimedes’ principle is the fundamental basis of naval architecture, stating that a statically floating body must displace a weight of water equal to its own total weight. Naval architects use this principle to predict a ship’s draft—the depth at which it floats—by ensuring the vessel's total weight, or displacement, is perfectly balanced by the weight of the water it displaces.12

To perform this calculation, architects estimate the sum of all weights, including the ship's structure, machinery, cargo, fuel, and crew. They then design the underwater hull volume to be sufficient to support this total weight. By dividing the total underwater hull volume by the volume per unit weight of the water in which the ship will operate, they determine the weight of the displaced water.123

Beyond simple depth, architects extend this principle to ensure the ship floats level and upright. By calculating the "moment arms" of both weights and buoyancy volumes, they ensure the centre of gravity and the centre of buoyancy are positioned to maintain static equilibrium and avoid unwanted heel or trim.24