The average cruise ship weighs from 20,000 to 60,000 tons, though cruise ship weights are usually calculated using gross registered tons. One GRT is equal to 100 cubic feet of enclosed revenue-earning space within the ship. On the GRT scale, modern cruise ships have an average weight of 100,000 GRT.
The 55 largest cruise ships in the world are all over 100,000 GRT. As of May 2014, the largest cruise ships in the world are Royal Caribbean's Allure of The Seas and Oasis of The Seas, weighing in at 225,282 GRT. The next largest is nearly 50 percent smaller at 155,873 GRT. Sizes trend upward, and the nine or more new cruise ships added each year since 2001 each weigh 100,000 GT or more.