Tŏn'nage, n.

(tŭn'nāj, 45), n. [From ton.]

1. The weight of goods carried in a boat or ship.
2. The cubical content or burden of a ship in tons; or the amount of weight which one or several ships may carry.

A fleet . . . with an aggregate tonnage of 60,000, seemed sufficient to conquer the world. Motley.

3. A duty or impost on ships, estimated per ton; or a duty, toll, or rate payable on goods per ton, transported on canals.
4. The whole amount of shipping estimated by tons; as, the tonnage of the United States. See TON.

☞ Tonnage in the United States is by law estimated as follows: for a double-decked vessel, take the length from the fore part of the main stem to the after part of the stern post above the upper deck; take the greatest breadth above the main wales, and reckon half this breadth for the depth; then deduct from the length three fifths of the breadth; multiply the remainder by the breadth, and the product by the depth, and divide this product by 95. For a single-decked vessel, the same as above, except that the depth is taken by measure from the under side of the deck-plank to the ceiling in the hold.