Light Ship Weight is the vessel as built: fully equipped but without cargo, ballast, fuel, fresh water, or stores. It includes the hull, machinery, accommodation, spares, boiler water, and engine lubricants. Because it’s fixed, it forms the baseline for all displacement calculations.
Displacement equals Light Ship Weight plus everything on board. Deadweight is the difference between the two. When only deadweight is shown in the ship’s tables, the light ship figure must be added back before applying density corrections. This avoids major errors in the survey.
Light Ship Weight also helps define the Constant, which represents all unknown weights such as added paint, rust, silt, and extra equipment. Since a ship becomes heavier over time, the Constant must be recalculated at each survey.
