How to calculate GRT for container ship if I know DWT?

-And for container ship, 1 GT (not GRT) = 1 DWT, is that correct?

Thank you.DWT is the dead weight of the vessel. It is the equivelent of the weight of the amount of water it displaces. (Archimedes Principle) GT or Gross Tonnage is a different value all together. GT is a calculation of the internal volume of the vessel. RT is the GT of the vessel deducted by the volumes of the spaces necessary for the working of the ship. (Engine room, Wheel house, galley space, ect).

Historically wine shipped to Britain was transported in large barrels called Tuns, the amount of tarriffs imposed was based on the number of Tuns that could be carried by a vessel. This is where the phrase Tonnage comes from when refering to the size of a vessel.



To calculate GT, the vessel needs to have many measurements. Length ways, sideways, and vertical. These measurements are taken at predetermined points and you use a calculus formula called Simpsons Rules to determine the internal volume of the ship. You then measure the deductable spaces and deduct those from the first amount to determine the registered tonnage.

I would have to write a small book to fully describe the process but hope this helps.