# Gross tons vs ITC

Does anyone know where i can get a straight forward easy explanation of the grt and ITC licensing rules. For example how many gross tons would 2259 ITC be?

Don’t know exactly but a 1600grt license is also 3000 ITC so it falls under a 1600 ton license

The difference is the way the boats ‘were’ admeasured. Back in 1970 (or so) the CG decided (at industry’s suggestion) to change the way vessels were measured.

I am sure you have seen the ‘tonnage doors’ on every vessel you have worked on? These were installed beginning in the early '70’s. They were the brainchild of architects to ‘make’ vessels measure ‘smaller’ than they really were. The CG went along with it. (All this was to make less stringent requirements concerning rescue equip., safety equip., hull construction, decreased height above waterline, etc etc etc.)

The simple explanation is: for every 100 cubic feet of interior volume ([I][B]in a water tight space[/B][/I]) is a ton. so by simple mathematical calculation you could determine the tonnage of a vessel.

Then the wizards of architecture came up with the grand idea that those bolt on doors did NOT classify as watertight, so any volume inside them was NOT included in the calculation. Note on a vessel with these doors, there is always bolt on door, after bolt on door, all the way to the forepeak, and including upper decks. This way NONE of the interior volume was included in the tonnage calculations! Also, note that NONE of these doors are below the waterline!

However, now saner heads have prevailed (foreign class societies) who we (the USCG) have agreed to adopt the REAL way to measure tonnage. This would be the ‘old fashioned’ way!

To return to your question, there is no easy calculation. It would have to be done by an architect.

Here’s a simple explanation. You have a filing cabinet that is 3.5’ X 3.5’ X 3.5’ Can you fit it through a door that is 3’ wide? Under GRT, you can if you take the drawers out.

There is no conversion for GRT to ITC. It varies based on the particular vessels as explained by cappy208. A problem with assuming an equivalency is the common case of a towing vessel that is 198 or 199 GRT. That seems to put it under the threshold of 500 ITC, but most of those vtugs are over 500 GRT. I’ve come across T-boatsd (passenger vessels under 100 GRT) that were over 2,500 ITC.

Inexact as any “equivalencies” are, for licensing purposes we had to establish a few critical ones as the US still uses GRT for regulatory purposes, but there are vessels that are only measured by ITC.

CG Policy Letter 15-02