tonnage
Refers to the capacity or weight of a ship measured in tons, or the total amount of cargo in tons.
The tonnage of this ship is 50,000 tons.
dead-weight tonnage
Standard kanji spelling for tonnage.
Common variant using katakana for トン.
Mixed kana-kanji spelling.
噸 is a kokuji (Japanese-created kanji) for 'ton', combined with 数 (number/amount).