Moorsom System

In 1849, the United Kingdom appointed a Commission with Mr George Moorsom as member and secretary to resolve these problems.^[1][2][3] The Commission determined that fees should be proportional to the earning capacity of the ship, whether for cargo or passengers.

The result was called The Moorsom System, which set forth the rules for the measurement of the internal volume of entire ship.

• The total internal volume in cubic feet (0.028 m³) was divided by 100 to produce the gross register tonnage.
• Net register tonnage was the volume remaining after subtracting the volume of the space used for machinery and other non-revenue producing functions.^[4]

The Commission sought to avoid a significant change in the fees charged to an existing vessel when the new system was implemented.

George Moorsom ordered the entire fleet of British merchant ships to be measured according to the new System and then divided the total gross tonnage by the total registered tonnage.

The result was 98.22 cubic feet (2.781 m³) per gross ton, which was rounded to 100 cu ft (2.8 m³) per ton.^[5]

While the rules for measuring ships changed over the years, the standard of 100 cu ft (2.8 m³) per ton remained in effect until a new system was established by The International Convention on the Tonnage Measurement of Ships, effective for new ships in July 1982.