Glossary term
Ship Draft
Vertical distance from the waterline to a vessel reference point, used to manage loading, clearance, stability, and performance.
Definition
quantityShip draft is the vertical distance from the waterline to the lowest hull or keel reference used for a vessel condition.
Draft links loading, displacement, water density, trim, under-keel clearance, port access, stability, resistance, propulsion immersion, and grounding risk. It must be interpreted with the loading condition, forward and aft marks, water density, trim, and measurement uncertainty.
Ship draft is the vertical distance from the waterline to a vessel reference point, usually the keel or lowest hull point. It is a direct operational indicator of loading condition, displacement, trim, under-keel clearance, and access limits.
Draft changes with cargo, ballast, fuel, stores, passengers, water density, marine growth, modifications, and damage condition. Forward draft, aft draft, mean draft, and extreme draft can differ, especially when a vessel trims by bow or stern.
Engineering use
Draft is used for port access, channel clearance, dry-dock planning, stability checks, loading manuals, propeller immersion, resistance prediction, sea-trial correction, grounding risk, and regulatory freeboard limits. It should be read with water density and loading condition because freshwater and seawater produce different drafts for the same vessel mass.
In operations, draft marks and loading software connect hydrostatic data with real vessel condition. A draft number without trim, density, and loading basis can be misleading.
Common mistakes
A common mistake is treating draft as one value when forward, aft, and maximum draft differ. Another is ignoring water density, squat, waves, heel, or dynamic motion when checking clearance. A strong draft review states loading condition, draft locations, trim, water density, under-keel clearance, measurement method, and uncertainty.