Editor’s Note: This will be part of a series that presents a few fun facts, figures and comparisons about cruise ships, and how to use them to help with making cruising decisions with your ToaD Travel Consultant.
When I board a ship for a cruise, I’m always interested in how roomy the ship is and how it will “feel” once I’m on board. I’m going to be there for a while and since I’m from the Midwest, I need a certain amount of personal space to feel comfortable.
Before I retired I used to do a lots of math. Now I’ve had some time to look at some interesting and simple calculations that help me to see how much elbow room I’m going to have on a cruise. It is a simple ratio that relates the total volume of the ship to the number of passengers. In simple terms, how much space can I expect?
This magic number is called the Passenger Space Ratio and it is easy to calculate to get a feel for how crowded you might feel on a certain class of ship. It is the simple ratio between the size of the ship (Gross Tonnage) and the number of passengers onboard. It is easy to compare with other ships since these two numbers are generally available across all cruise lines. At least now we can compare apples to apples.
About the numbers involved… Gross Tonnage (gt) is a bit of a math nightmare, and doesn’t really have anything to do with the weight of a ship. Instead, it is a measure of all of the enclosed spaces within the ship. There is a lot of history (and math) behind it, but all we really need to know is that it is a “fair” number that makes a good attempt to represent all ships properly for all sizes and usages. Since we only care about cruise ships, all of that math is done.
Since we usually don’t know how many guests will be on any given cruise ahead of time, we need to have a ‘standard’ number of passengers for each ship. It’s nice that almost all ships have a capacity number that is generally the number of staterooms with two occupants in each. This is sometimes called the ship’s capacity or double occupancy. The ship may hold many more people if every single bed, bunk and berth is occupied, but double occupancy is a reasonable number to use for comparisons, and is often used by cruise lines to determine a “full ship.”
Finally, we can calculate the Passenger Space Ratio. It is simply the amount of space on the ship divided by the number of passengers. There, done. If we only had a table with some of these values filled in, it would be interesting to see how different cruise line ships have designed, built and outfitted their ships and how each design, level of luxury and service offered changes this ratio.
The following table shows the gross tonnage, number of passengers (double occupancy) and the calculated passenger space ratio for several ship classes across several cruise lines.
Many ships fall within a reasonably close range, and some ship design features will affect this number. For instance, Royal Caribbean’s Oasis of the Seas has a Boardwalk and Central Park areas that are within the confines of the ship, but since they are open to the sky the space is not include in the Gross Tonnage figure. On the other hand, the atmosphere of having a few birds along for the ride and having an open park-like setting to eat lunch is amazing.
If you are looking up the Gross Tonnage for yourself, be sure that it is the Gross Tonnage, and not one of the other similar numbers that only help with the confusion (Gross Register Tonnage, Net Register Tonnage, Displacement, Compensated Gross Tonnage, etc.). Gross Tonnage is the number to use for all ships built after July 18, 1982, but sometime sources may round up, or the number could change over time if the ship has a major upgrade during dry dock that affects the number of passengers or the volume of enclosed space within the ship.
I wouldn’t make a decision to not go on a ship because the Passenger Space Ratio seems too low, or is a few hundredths lower than another ship, but it is useful.
Remember that there are several other numbers and statistics that we can look at that give us more information on everything from how a ship will ride in rough weather, how many crew are there to serve you, and a host of other things that can be compared across cruise line, ship classes. Taken together these can help to give an improved perspective on what you can expect on your cruise.
