GT vs NT: Why a Vessel Has Two Different Tonnage Numbers

Every vessel carries two tonnage figures — GT and NT — that look similar but measure different things. Here's what each one means.

In vessel documents, certificates, and technical specifications, two figures almost always appear side by side: GT (Gross Tonnage) and NT (Net Tonnage). Neither is a measure of weight — despite the word "tonnage" — they're both volume measurements, and each measures something different.

Gross Tonnage (GT)

GT measures the total volume of every enclosed space on the vessel — cargo holds, engine room, crew accommodation, and every other enclosed compartment. It's calculated using the formula set by the International Convention on Tonnage Measurement of Ships, 1969 (ITC-69), and serves as the primary reference for vessel categorization, port fees, and applicable regulatory and safety requirements.

Net Tonnage (NT)

NT measures the volume of space actually used for carrying cargo or passengers — in other words, the vessel's commercially "productive" capacity. It's derived from GT minus spaces that don't generate direct revenue, such as the engine room and crew accommodation. NT is therefore always smaller than GT.

Why the Difference Matters

GT is generally the basis for port fees, safety certification requirements, and regulatory size classification. NT is more relevant to commercial capacity calculations. TB. CHANNEL, one of the vessels we operate, has a GT of 26 and an NT of 8 — that gap reflects how much of a small tugboat's volume is engine room and accommodation relative to genuinely productive space.

See the Fleet page for full technical specifications for TB. CHANNEL and TK. CIPTA ABADI, including each vessel's GT/NT.