What is Gross Registered Tonnage?

Voyager of the Seas Facts

Voyager of the Seas Facts

Visit any website or read any brochure that details passenger cruise vessels, and you will often see a small list of ship facts somewhere, and one of those facts is something called “gross registered tonnage”, abbreviated GRT.  Why the heck would you need to know how much the ship weighs, and how on Earth do they even calculate that??

It’s Not About Weight

For starters, the gross registered tonnage is not a measure of the weight of the ship.  Rather, it is a measurement of the revenue-producing areas of the ship, where 100 cubic feet of space equals 1 gross registered tonnage.  This measurement is used to determine what port fees the cruise line will pay for that ship to dock at a particular port.  A larger GRT value means more revenue-producing space, which means a larger ship, which means higher port fees.

I know what you’re thinking now – if this is something that is used for cruise line operations, why would the average passenger be concerned with it?

Space Ratio

Some people like really large ships, such as Royal Caribbean’s Oasis of the Seas.   Other people are spooked by the idea of cruising with so many people at the same time, feeling they would be crowded onto the ship like sardines in a can.  But, just because a ship is large does not mean it is crowded.  You can get an idea of how much space there is per passenger by determining the ship’s space ratio.  Here’s the simple formula:

Gross Registered Tonnage
——————————–   = Space Ratio
No. of Passengers

Obviously, a higher space ratio means there is more space per passenger, and therefore is less crowded.  Most cruise vessels are in the mid-to-high 30’s; some luxury or premium lines are at 40 or higher.  If you are due to sail on a vessel that is less than 36, be prepared to be cramped!


  1. Steve…I never knew how the cruise lines figured their space ratio per client. This is very useful information, handy when explaining gross tonnage to my male clients. I never knew it had anything to do with port fees and revenue-producing space. Useful for us cruise agents…and you explained it perfectly…thank you!!

    Patti Maxwell

  2. This is a great explanation of what GRT means. It’s a good fact to know especially for those of us who don’t like to feel crowded.

  3. 100 cubic feet = 1 gross registered TON. Not 1 gross registered tonnage.

    • Steve Cousino says:

      That’s where a lot of folks get confused, actually! There’s actually nothing being weighed, therefore there are no real “tons” involved to speak of. It is a calculation of the space available. But, thanks for your comment!