Measurement and Tonnage Laws


Measurement of vessels: On May 6, 1864, Congress passed an act that practically adopted the gross tonnage measurement system established in Great Britain by the Merchant Shipping Act of 1854.

The act of 1864 was amended by the act of February 28, 1865, which provided (Rev. Stat. 4151) that no part of any vessel used for cabins or staterooms and constructed entirely above the first deck which was not a deck to the hull, should be required to be measured or registered for tonnage.

This amendment was drafted particularly for coastwise, lake, and river steamers but also applied to ocean steamers.


Tonnage Statutes

According to the interpretation made by the United States Customs Regulations of 1908 (Articles 71-87), this amendment "was designed merely to exclude cabins and staterooms above the promenade deck of the steamers of the seacoast and lakes, or above a boiler deck as used on the western rivers. It does not have the effect of exempting from admeasurement any closed-in place even if so situated if used for cargo and stores."

The act of 1864 provided only for the ascertainment of gross tonnage, and until 1882, this formed the basis upon which tonnage taxes and ship charges were levied at American ports.

In 1882, the United States Measurement Act adopted the Danube Rule, which, in the case of most ships, made a smaller allowance for propelling power, including fuel, than the British Act.

The act of 1882 was superseded by the Frye Measurement Act of March 2, 1905, which adopted the British rules for measuring propelling power for the United States, bringing our measurement laws into accord with prevalent maritime practice. On February 6, 1909, another act dealing with tonnage was passed.

Under present United States laws, regulations, and interpretations, the tonnage basis for charges on an American ship does not exceed that on a foreign vessel and, in some cases, is materially less.


Rules of Measurement

The United States gross tonnage rules include in the measurement the entire space under the tonnage deck and between the tonnage and upper decks; the space occupied by hatchways over one-half of one percent of the vessel's gross tonnage, exclusive of the hatchway tonnage; and any permanent closed-in space on the upper deck available for cargo or stores or for the berthing or accommodation of passengers or crew.

Under the law of 1865, however, as has been stated, certain passenger decks are not subject to gross tonnage measurements.


Nine different spaces are exempt from gross tonnage measurement. They are:

  1. Double-bottom water-ballast spaces are not available for stores or hulls, and the spaces between the frames and the floor beams.
  2. Spaces under the shelter deck and in the poop, forecastle, and bridge when not permanently closed in.
  3. Passenger accommodations in tiers of superstructures over the first tier above the upper deck.
  4. Hatchways up to one-half of one percent of the vessel's gross tonnage.
  5. Galleys, bakeries, toilets, and bathhouses above deck.
  6. Spaces above the deck occupied by the ship's machinery or for the working of the vessel.
  7. Light, air, and funnel space over the engine and boiler room and above the upper or shelter deck.
  8. Domes and skylights, companionways (except portions used as smoking rooms), and ladders and stairways in exempted places.
  9. Open spaces occupied by deck loads.


American Tonnage Rates

Tonnage Duties: These are a general charge or tax on shipping and are closely related to the measurement of vessels. Practically all countries levy them.

In the United States (Rev. Stats. 427, amended by sec. 36, act of August 5, 1909), a tonnage tax at the rate of two or six cents for each net ton is levied upon every vessel engaged in trade upon arrival by sea from a foreign port. Ships in distress are exempted.

The two-cent-a-ton rate applies to all vessels arriving from any foreign port in North America, Newfoundland, Central America, the West Indies, the Bahamas, and Bermuda, or the coast of South America bordering on the Caribbean Sea.

The six-cent a-ton covers all vessels arriving from any other foreign port. The tonnage duty is not levied on more than five entries at the same rate during any one year, the tonnage year beginning with the date of the first payment and ending on the day preceding the corresponding day in the following year.

United States tonnage rates are about the same as the light dues imposed in Great Britain. They are considerably lower than those levied in the ports of Continental Europe and elsewhere.

United States laws make various exemptions from the payment of tonnage duties. These primarily affect the fisheries and the Great Lakes vessels.


Bankers Trust Company, "Chapter XXIII: Measurement and Tonnage Laws," in America's Merchant Marine: A Presentation of Its History and Development to Date with Chapters on Related Subjects, New York: Bankers Trust Company, 1920, pp. 183-185.


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