# Grt vs gt

Is there a way I can extrapolate grt from gt? I’ve seen that it is vessel specific so I guess I’m wondering if there is a ballpark formula for tugs specifically

[QUOTE=Hawesclaws;125684]Is there a way I can extrapolate grt from gt? I’ve seen that it is vessel specific so I guess I’m wondering if there is a ballpark formula for tugs specifically[/QUOTE]

GT divided by Green = GRT… the more green you have, the smaller GRT becomes. That’s bayou math, it might be different in other parts of the world.

Check your documentation, if it does not include a GRT/GT tonnage, your vessel does not have one. What are you trying to accomplish?

One register ton (RT) is equivalent to 100 cubic feet. Thus, the gross register tonnage can be calculated directly from the gross volume. Gross tonnage, on the other hand, is calculated from the gross volume (in cubic metres) with a mathematical formula. You can calculate the gross tonnage from the gross register tonnage by substituting V with GRT and applying a suitable conversion for the units:

GT = GRT * [0.0616 + 0.0071 * log10(GRT))]

For back-calculating GRT from GT, I would recommend typing the formula into e.g. Excel.

However, why are you interested in calculating the gross register tonnage? It’s no longer in use. If the ship’s gross tonnage is known, use that instead.

Trying to figure out if a 150gt vessel qualifies as a 200grt vessel because the rfpnw full endorsement requires half of the 180 days to be on a 200grt vessel or above.

[QUOTE=Hawesclaws;125696]Trying to figure out if a 150gt vessel qualifies as a 200grt vessel because the rfpnw full endorsement requires half of the 180 days to be on a 200grt vessel or above.[/QUOTE]

Probably not. Generally, GT is higher than GRT. The difference is that GRT excludes certain spaces from the volume calculation that GT does not. This is why it’s vessel specific and there is no conversion formula, ikt depends on how many of those GRT excluded spaces are on the vessel. For mariner credntial putrposes, the Coast GHuard has considered 200 GRT to be equivalent to 500 GT and 1,600 GRT to be equivalent to 3,000 GT. These are the only two such equivalencies, we do not interpolate a linear relationship between these two points.

An overly simple way to think of GRT vs. GT is to consider a filing cabinet 3.5’ x 3.5’’ x 3.5’. Is there any way to get that through a door that is 3’ wide? Under GRT, you could if you took the drawers out.

[QUOTE=“Ea\$y Money;125686”]

GT divided by Green = GRT… the more green you have, the smaller GRT becomes. That’s bayou math, it might be different in other parts of the world.[/QUOTE]

That is funny.

Thank you again Mr cavo for shedding light. I understand the 200gst 500 gt relationship in the wording now. Snails pace but I am learning thanks to folks such as yourself and thus forum.