Moulded depth is the vertical distance measured along the vessel's transverse plane from the top of the keel plate (excluding its thickness) to the underside of the main deck plating (excluding its thickness). In simpler terms, it's the depth of the ship's hull, measured from the top of the keel to the bottom of the main deck.

This measurement is crucial in naval architecture and shipbuilding as it influences a ship's stability, cargo capacity, and overall structural integrity.