I have a question about Gross Registered Tonnage for Mariner Licensing. A good portion of my sea time is on a private yacht that just shows Gross Tonnage on the COI, not Gross Registered Tonnage. Is there a formula used to determine Gross Registered Tonnage for a vessel for Mariner Credentials? Thanks in advance,

Here is what I have used for CG 719S Sea Service Form.

A simplified set of gross tonnage formulas is set forth by the U.S. Coast Guard Marine Safety Center, which are based on three measurements: Length (L), breadth (D), and depth (D). Under this system, the means of estimating gross tonnage is as follows:

For power boats: Gross Tonnage = (. 67 x L x B x D) / 100.

For a sailing boat with keel, Gross Tonnage = (.375 * L * B * D) / 100

For freighters with angled or cylindrical hulls, Gross Tonnage = (.67 * L * B * D) / 100

For ships with square barge-shaped hulls, Gross Tonnage = (.84 * L * B * D) / 100**

For a boat with a simple sailing hull, Gross Tonnage (GT) = (.5 x L x B x D) / 100**

Thanks for all of the great information. So if I am working an a vessel thatâ€™s only calculated with the simplified tonnage, how does this type of Vessel Gross Tonnage work when looking to upgrade your license when the Sea Service for the vessels needs to be in Gross Registered Tonnage? I attached a picture of the specs on the vessel along with a license checkoff list. Thanks for all of your help.

Thanks for the information. Would the 137 Gross Tons vessel I work on satisfy a Sea Service requirement thatâ€™s calling for time on vessels of 100 GRT or more? Thanks again.

The formulas I provided earlier were based on both the CFR and Simplified Measurement Gross Tonnage Guide to comply with the guidance for filling out the 719S form found in Documenting Sea Service on the NMC website. Based on my reading NMC is calculating Gross Tons as GRT. I believe that they will calculate for you given the Length, Beam and Draft based on the vessel type.