Given its massive size, how fast does a cruise ship travel? For those built for speed, the answer is about 30 knots per hour. For cruise ships in general however, it's around 21 to 24 knots, which is still pretty fast all things considered.
Size and Speed
It's all about the numbers. To start, consider that one ton is equal to 2,000 pounds and that cruise ships can weigh up to 71,500 tons, which is 143,000,000 pounds. This raises two obvious questions:
How can something so enormous float? - How can something that large travel so fast on water?
In regards to question one, the key is displacement. Centuries ago, engineers figured out that a ship can remain afloat by displacing the water it's immersed in. This buoyancy can be maintained up to a point, so long as the balance between vessel and water remains intact.
As for question two, gas-turbine or diesel-electric engines power cruise ships, while propellers provide the movement. The turning action of propellers cuts through water and propels the ship either forward or backward. Most modern cruise ships are able to achieve speeds of 21 to 24 knots, which is 21 to 24 nautical miles per hour or 24 to 27 miles per hour.
Fuel Consumption
As for the fuel needed to move a cruise liner, the numbers are again remarkable. In the world of cruise ships, mileage isn't measured in miles, but in feet. So, how far can a cruise ship travel on 12.5 gallons? For the Queen Elizabeth 2, the answer is 625 feet. Note that the ship itself measures 963 feet in length.
How Fast Does a Cruise Ship Travel?
In the above example, the Queen Elizabeth 2 was a vessel built for speed and thus, her mileage is unlike most other ships. While her top speed can reach 32 knots, most ships typically sail at 20 knots per hour.
Even if ships can go faster, say 23.5 knots, they may choose not to in order to conserve fuel and pace their voyage. Cruise ships travel at a speed that gets them to their destination and back. They also all travel to different ports. Thus, their individual routes are a major variable.
If a port is close, a ship will take its time to reach it. It might even float or idle for some time. However, if the destination is a fair distance away, a ship will pick up speed when out in open waters. Ships have both a top speed and a service speed.
Thus, in response to the question, "How fast does a cruise ship travel?" there isn't one definitive answer. Each ship is different; although the average speed remains about 21 to 24 knots. Smaller ships, like economy cars, will get better mileage than big cruise ships. Yet, the difference is only a few knots more. Speed vessels, like the QE2 and the Olympic Voyager from Royal Olympic Cruises, are rare.