Ship measurements like DWT, GRT, and NRT refer to the weight and volume of a ship. DWT is the weight of cargo, fuel, and supplies that a ship can carry, showing its revenue potential. GRT and NRT measure the total and cargo-carrying volumes, respectively, of enclosed spaces on a ship. Understanding these metrics is important for ship owners, operators, and clients.

1. Ship Measurement
DWT, GRT, NRT, etc….
http://www.themaritimesite.com/a-guide-to-understanding-ship-weight-and-tonnage-measurements/

2. Hi light
watertank fueltank cargotank machine,frame&plate enclosedspacefortransportedcargo enclosedspacefornontransportedcargo
Displacementtonnage
StandardDisplacementtonnageSDT
DeadweighttonnageDWT
LightweighttonnageLWT
GrossregisteredtonnageGRT
NetregisteredtonnageNRT
Volumebased100cubicfeet=1tonWeightbasedmeasurement

3. Displacement Tonnage
Displacement tonnage is nothing more than the total weight of the volume of water a ship
“displaces” when it is sitting in the water.
Imagine you had a large bucket filled to the brim with water. Now, suppose you gently
placed a basketball in the bucket causing some of the water in the bucket to spill out.
Once the basketball had stabilized and was freely floating in the bucket, the weight of the
water that was “displaced” is equal to the “displacement” (or weight) of the basketball.

4. Standard Displacement Tonnage
Standard displacement tonnage is basically the same thing as “displacement tonnage”
with one minor difference. When calculating standard displacement tonnage, you subtract
the weight of any fuel and potable water carried on board the ship.

5. Dead Weight Tonnage
Deadweight tonnage is the weight (in tons) of all the cargo, fuel, dry provisions, supplies, etc.
carried on board the ship. In other words, it is the “displacement tonnage” of the vessel minus
the “lightweight tonnage” (see lightweight tonnage below). Deadweight tonnage is a good
indication for ship owners and clients of how much revenue the vessel is capable of generating.

6. Light Weight Tonnage
Lightweight tonnage is best described as the weight of the ship when it was built in the shipyard
including all framing, machinery, decking, etc. However, lightweight tonnage does not include
the weight of any consumable such as fuel, water, oil, or supplies.

7. Gross Registered Tonnage
Gross registered tonnage is a measurement of volume of all enclosed spaces on a ship with 100
cubic feet = to one ton. For instance, if the total cubic volume of all the enclosed spaces on
a ship were 340,000 cubic feet, the gross registered tonnage will most likely be 3400 gross tons
(340,000 cu. feet/100 cu feet/ton = 3400 Gross Tons).
Gross Tonnage or “Gross Tons” is what you’ll see most often on official ship documents and
certificates, but you’ll also set “net tons” and “deadweight tons” (expresses DWT) used from
time to time.

8. Net Weight Registered
Net registered tonnage is also a measurement of volume however you only consider the volume of
actual cargo storage areas when dividing the cubic volume in feet by 100 to get your “tonnage”. This
includes any tanks, cargo holds, etc. that are normally used for transporting cargo.