The draft (or draught) of a ship's hull is the vertical distance between the waterline and the bottom of the hull (keel), with the thickness of the hull included; in the case of not being included the draft outline would be obtained. Draft determines the minimum depth of water a ship or boat can safely navigate.The draft can also be used to determine the weight of the cargo on board by calculating the total displacement of water and then using Archimedes' principle. A table made by the shipyard shows the water displacement for each draft. The density of the water (salt or fresh) and the content of the ship's bunkers has to be taken into account. The closely-related term "trim" is defined as the difference between the forward and after drafts.
The draft forward (bow) is measured in the perpendicular of the bow.
The mean draft is obtained by calculating from the averaging of the stern and bow drafts, with correction for water level variation and value of the position of F with respect to the average perpendicular.
Variations of the draft
The draft of a ship can be affected by multiple factors, not considering the rise and fall of the ship by displacement: