deadweight

A common measure of ship carrying capacity. The number of tons (2240 lbs.) of cargo, stores and bunkers that a vessel can transport. It is the difference between the number of tons of water a vessel displaces "light" and the number of tons it displaces "when submerged to the 'deep load line'." A vessel's cargo capacity is less than its total deadweight tonnage. The difference in weight between a vessel when it is fully loaded and when it is empty (in general transportation terms, the net) measured by the water it displaces. This is the most common, and useful, measurement for shipping as it measures cargo capacity.