Air Draught
The vertical distance from the waterline to the highest point of the ship: what must clear under bridges and cranes.
- Category
- Vessel Size and Tonnage
- Last reviewed
How it works
Air draught is the height of a vessel above the water: from the waterline to the top of the mast or other highest fixed point. It changes with loading, since a more laden ship sits lower.
It is the critical clearance figure for passing under bridges, power lines and gantry cranes; an under-estimated air draught is a recurring cause of bridge allisions.
Where it shows up on The Maritime
Also known as: air draft, overhead clearance.
Related terms
Draught
The vertical distance from the waterline to the bottom of the keel: how deep the ship sits in the water.
Load Line
The set of marks on a ship’s hull showing the maximum permitted loading draught for different water densities and seasons.
More vessel size and tonnage terms
A plain-English reference definition: our own explanation of a standard shipping concept, not a licensed source or legal advice. See the full glossary or the broader maritime dictionary.
Last reviewed: .