Gross Tonnage of a Cruise Ship – What Does It Mean?

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The fact that cruise ships can host thousands of passengers and crew members at the same time, all while floating on the water, is truly fascinating.

This becomes all the more interesting when you consider that these floating behemoths are outfitted with state-of-the-art amenities, varied dining establishments, and luxurious accommodations. When you think about it, the scale of a modern cruise ship almost boggles the mind. 

When discussing the size of a cruise ship, you may come across terminology that refers to the “gross tonnage” or “gross tons” of a boat. To those with a limited understanding of maritime terminology, these words may not hold much meaning. To help you understand what they mean, we will take a deep dive into the meaning and relevance of gross tons for cruise ships. 

Not only will we explain the meaning and the formula used to calculate this measurement, but we’ll also dive into the relevance of the phrase for cruise ship passengers. Learn what gross tonnage means and why it is important for the cruise industry.

What Does Gross Tonnage Mean?

Gross tonnage is a type of measurement used across the maritime industry. It is used to quantify the internal volume of a vessel. Given the name and the fact that a ton is used to measure 2,240 pounds of weight, many people assume that a ship’s gross tonnage is simply a measurement used to describe the total weight of a cruise ship

Instead, it calculates a ship’s internal space using “gross tons,” or GTs, as the primary unit. A gross ton is equivalent to an internal volume of 100 cubic feet.

So, if a cruise ship had an interior closed space of 200 cubic feet, it would have a total of two gross tons. This is different from net tonnage, which is the gross tons minus the space occupied by the engine room, fuel, navigation machinery, and crew quarters.

While it may seem like a fairly insignificant measurement for anyone other than the ship’s designers, we will explain later why gross tonnage is far more than a simple technical detail in ship design.

We’re going to take a good look at gross tonnage here, but there are actually a few different types of tonnage to be aware of when it comes to ships, including: 

  • Gross tonnage 
  • Net tonnage
  • Deadweight tonnage, the weight of the ship’s contents, including its fuel, crew, passengers, food, water, and cargo
  • Displacement tonnage, the volume of water displaced by the ship at sea
  • Lightship weight tonnage, the weight of the ship plus its permanent equipment; this doesn’t count supply, water, or fuel

How Is Gross Tonnage Calculated?

Since measuring internal space in a cruise ship is difficult, given the unique dimensions and proportions, the formula used to calculate its gross tonnage is fairly complex.

Just think how difficult it would be to add all the space in every single internal area in a ship, including passenger cabins and crew quarters, dining halls, public amenities, the engine room, the bridge, and even the lower cargo holds.

Cruise Ship During Dry Dock
Cruise Ship During Dry Dock (Photo Credit: MartinLueke)

If you are interested, the calculations use the following formula: Gross Tons (GT) = K1V, where V is the volume of the ship’s internal space in cubic meters and K1 is 02 + 0.02. 

As we said, it’s a little complicated, but don’t worry, nobody will ask you to calculate this unless you choose to become a marine engineer or naval architect. The main takeaway is that gross tonnage is a measurement of the internal space of a ship rather than its total weight out of water. 

Why Is the Measurement of Gross Tonnage Important for Cruise Ships?

Aside from a practical need to understand how much interior space a cruise ship has, the gross tonnage of the ship plays an integral role in meeting various guidelines and safety regulations. 

Like other types of large-scale vessels, like cargo ships and oil tankers, cruise ships have to abide by various international standards laid out by the International Maritime Organization, or IMO.

TUI Cruises Mein Schiff 7
TUI Cruises Mein Schiff 7

Not only do they have to adhere to standard rules regarding stability, but cruise ships must also meet specific safety standards for all passenger ships. Many of these safety standards and regulations relate heavily to the ship’s gross tonnage. 

Along with passenger capacity and the vessel’s length, width, and height, gross tonnage is one of the leading figures used to assess the size of a cruise ship. Many of these safety standards and regulations relate heavily to the ship’s gross tonnage. 

Gross Tonnage and the Safety and Stability

Gross tonnage is related to buoyancy, as it measures the amount of interior space the ship has available. To carry a specific amount of weight, a ship must have the appropriate amount available while still maintaining stability in open waters, even if it is traversing rough waters.

Cruise Ship Hurricane
Cruise Ship Hurricane (Photo Credit: PHkorsart)

Along with other regulatory bodies, the International Maritime Organization has specific regulations that regard a cruise ship’s gross tonnage. For example, any cruise ship with a gross tonnage of 500 or more GTs must adhere to various environmental standards.

There are countless other ways gross tonnage is used to assess compliance with various regulations. Some of these regulations concern the environment, while others are related to the types of equipment that the ship must be outfitted with. 

Gross Tonnage for Docking Procedures and Port Fees

Since gross tonnage gives a more accurate picture of a ship’s size and proportions than weight, port authorities and port pilots need an accurate measure of a cruise ship’s gross tonnage before it is allowed into a port.

Cruise Ship Pilot
Cruise Ship Pilot: (Photo Credit: Stories In Light / Shutterstock)

Not only does this figure determine where and how a cruise ship will be able to dock, but it is also a measurement that plays a vital role in determining how much the cruise line that owns the ship will be charged in port fees and other charges. As you can imagine, larger ships with a greater gross tonnage tend to owe larger fees for using a port

A cruise ship’s gross tonnage is also an important figure for charting a cruise ship’s route and itinerary. Since larger ships can be prohibited from certain waters, accurately understanding the ship’s gross tonnage will inform the navigation crew where they can take the ship. 

How Does Gross Tonnage Impact Passenger Capacity?

While it may sound fairly obvious, a cruise ship’s gross tonnage will determine how many passengers it can carry and how many crew members it will need to operate safely. Ships with a greater gross tonnage can accommodate more passengers and offer more space for amenities, like dining areas, pool facilities, and more.

Royal Caribbean Passengers
Royal Caribbean Passengers

The world’s largest cruise ships have the greatest amount of gross tonnage. More importantly, they have more of this space that can be dedicated to passenger use. In addition to carrying more passengers and having more entertainment options, larger ships can offer a more comfortable experience for those carrying. 

How Does Gross Tonnage Impact Passenger Comfort and Entertainment Options?

Naturally, larger ships tend to have more options available to passengers. The ship’s designers have more space to work with when choosing which onboard amenities and facilities will be available to passengers. They can also afford to offer larger cabins and suits, as the ship can afford to dedicate this space to private quarters. 

What may surprise you, especially given how top-heavy they can look, is that larger cruise ships with a greater gross tonnage tend to be more comfortable and stable than smaller vessels.

If you have a history of suffering from motion and seasickness, you may want to opt for a larger cruise ship when booking your next cruise vacation. 

Cruise Ship Stabilizer
Photo Credit: Dave R

Not only do larger ships displace water more effectively, which helps reduce the rocking sensation that causes seasickness, but they are also outfitted with more extensive and more effective stabilizers.

Imagine cruise ship stabilizers like giant wings that protrude outwards beneath the water. The larger these stabilizers are, the more effective they resist waves that would otherwise cause the ship to roll.

On top of that, larger ships also have more sophisticated gyroscopic stabilizers, making the ship more adaptable to changing sea and wind conditions. 

While larger ships have their advantages when it comes to providing more entertainment options, larger and more varied accommodations, and a more comfortable passenger experience, you must remember that gross tonnage can impact a cruise ship’s ability to travel through certain waterways.

Royal Caribbean Ships by Age
New and Old Royal Caribbean Cruise Ships (Photo Credit: Darryl Brooks / Shutterstock)

While they may be somewhat limited in the amenities they can offer, the operators of smaller vessels have more flexibility when planning their ship’s itinerary. Plus, smaller cruise ships tend to pay reduced port fees; however, from a passenger perspective, this might not impact your price because those port fees will be spread across fewer people on a smaller ship. 

Frequently Asked Questions

What is the average gross tonnage of a cruise ship?

While gross tonnage will vary quite substantially from one cruise ship to the next, the industry average gross tonnage is 120,000 GTs. 

For perspective, Royal Caribbean International’s Explorer of the Seas is considered an average-sized cruise ship with a gross tonnage of 137,308 GTs.

This translates to a total passenger capacity of 4,290 passengers and 14 decks. While impressive, it is still much smaller than some of the world’s largest cruise ships, like Royal Caribbean’s Symphony of the Seas. 

Which cruise ship has the greatest gross tonnage?

Royal Caribbean International operates the cruise ship with the greatest gross tonnage in the world – the Icon of the Seas. This revolutionary cruise ship has a total gross tonnage of 250,800 GTs

Given its immense proportions and the incredible amount of internal space the ship offers, the Icon of the Seas raises the bar regarding onboard entertainment and amenities. Amongst other mind-blowing amenities, it boasts the largest water park ever seen on a cruise ship and the world’s tallest water slide. 

What does the deadweight tonnage of a cruise ship mean?

While they may sound like fairly similar measurements, the deadweight tonnage of a cruise ship differs from its gross tonnage. Where gross tonnage refers to the internal space of a cruise ship in 100 cubic feet units, the deadweight tonnage refers to the weight the cruise ship can safely carry. 

This measurement excludes the weight the ship must carry in the form of engine components and other vital pieces of equipment. Instead, it refers to the weight the vessel can carry in cargo, fuel, supplies, passengers, and passenger luggage. In other words, the weight will vary each time the ship departs. This is why you may notice that everything is meticulously weighed when you board a cruise ship.

How is gross tonnage measurement standardized across the cruise industry?

Since measuring the gross tonnage of a ship is so important for assessing adherence with certain international regulations and determining what a ship will owe in port fees, it is essential that determining the measurement is standardized and that gross tonnage measurements are reported accurately. 

To ensure accuracy, all cruise lines must submit gross tonnage calculations using the International Maritime Organization’s International Convention on Tonnage Measurement of Ships Formula. This was made mandatory in July of 1982 and included a standardized formula for measuring a ship’s deadweight tonnage.

Given that the IMO set out this rule, failure to use these standardized calculations can result in significant fines and other punishments for the cruise line that was proven to be in violation. 

Final Words 

While a cruise ship’s gross tonnage may seem like a fairly trivial measurement from a passenger perspective, it is one of the most useful and important measurements used within the entire maritime industry, including the cruise industry.

Read Also: How Ship Draft Affects a Ship’s Performance

Gross tonnage accurately measures a ship’s internal space and determines how stable and safe the cruise ship will be once it is out on open water. As cruise ship designers continue to innovate and release even larger cruise ships, this measurement will remain relevant across the entire industry.

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