Vessel Size and Tonnage Terms
How a ship is measured and classed: the tonnage figures behind every freight and valuation comparison, the draught limits that shape trading, and the size bands the market quotes.
Aframax
A crude and product tanker class named for the Average Freight Rate Assessment scale, sized for regional and medium-haul trades.
Air Draught
The vertical distance from the waterline to the highest point of the ship: what must clear under bridges and cranes.
Ballast
Seawater carried in tanks to keep an unladen ship stable and properly trimmed; also the term for a non-revenue, empty leg.
Capesize
The largest standard dry-bulk carrier, too big for the Panama and Suez canals and so routed around the Capes.
Deadweight Tonnage (DWT)
The total weight a ship can carry (cargo plus fuel, stores, crew and water) at her load line, in metric tonnes.
Draught
The vertical distance from the waterline to the bottom of the keel: how deep the ship sits in the water.
Gross Tonnage (GT)
A dimensionless measure of a ship’s total internal volume, used for regulation, manning and port-due calculations.
Kamsarmax
A dry-bulk carrier sized to the maximum length that can load at the port of Kamsar in Guinea, one step above the classic Panamax.
Laden
The state of a ship carrying cargo: the revenue-earning leg of a voyage, and the opposite of ballast.
Load Line
The set of marks on a ship’s hull showing the maximum permitted loading draught for different water densities and seasons.
Net Tonnage (NT)
A volume-based measure of the space available for cargo and passengers, derived from gross tonnage.
Panamax
A ship sized to the dimensional limits of the original Panama Canal locks; in dry bulk, the class just below Kamsarmax.
Suezmax
A crude tanker sized to the maximum that can transit the Suez Canal fully laden.
Very Large Crude Carrier (VLCC)
A crude oil tanker in the largest actively traded class: the backbone of long-haul Middle East to Asia oil transport.
Where these terms show up on The Maritime
About these definitions. Plain-English reference definitions of standard shipping concepts: our own explanations, not legal advice. Each term page opens with the definition, explains how the concept works and links to the desk where The Maritime measures it. The first entry is Aframax.
Glossary last reviewed: .