How fast is a 'knot' and why is it called that?

If you’ve been on a cruise and found yourself unfamiliar with the navigation terminology, you’re not alone! Understanding terms like knots and nautical miles are not necessarily intuitive for most cruisers. 

Your cruise ship captain probably referenced the ship’s speed using knots. Perhaps the captain also mentioned how many nautical miles until your next port of call. 

Why can't we use standard terminology like miles or kilometers per hour? To start, travel on land has landmarks that can be used for navigation. Before technology, travelers relied on landmarks to get where they needed to go.

At sea, there are no landmarks that can be relied upon. As such, sailors have to rely on longitude and latitude at sea to ensure the correct navigation is achieved.

But, how fast is one knot and why do we call it that?

Let’s dive in! 

Definition

Answering these questions will require us to define a few basic nautical terms. 

The formal definition of a knot is a form of measurement that equals one nautical mile. This is used to measure the speed of your cruise ship. Of course, this isn’t very helpful unless you also understand what a nautical mile refers to.

Nautical mile refers to the distance traveled by your cruise ship, which is a bit longer than a land-based mile. This is measured between two points of latitude on the globe. This type of measurement is used because of the Earth’s curvature.

Essentially, knots are used to measure speed and nautical miles measure distance. One knot is equal to one nautical mile per hour. With a little conversion, we find that one knot is equal to 1.15 land-based, or statute, miles per hour.

For reference, most cruise ships travel around 20 knots per hour, which is roughly 23 land-based miles per hour. 

However, the above is just an average. The mega ship Oasis of the Seas, for instance, has a high speed of 24.5 knots per hour, or 28.2 miles per hour.

If you find yourself curious about your current speed when onboard, most cruise lines have a channel on their stateroom television's that provides this information. It's quite interesting to compare speeds during the day to speeds at night! 

History of Knot

Now that you know a little history on the nautical mile, you might be wondering why we call the speed measurement a knot. 

Back in the 17th century, sailors coined the term ‘knot’ as a measurement of their speed using a device called a “common log”. This was a handy device used on the ship that consisted of a log with a rope and knots at regular intervals. The knots were attached to a piece of wood that was shaped as a triangle.

History states that sailors would lower the common log, covered in rope with knots, into the sea. The common log would float freely along the vessel for a specific amount of time. Often times, a sailor onboard the ship would watch the time by using an hourglass. Once the time was finished, the sailors would count the knots between the ship and the piece of wood. This was used as their speed calculation. 

Hence, the term knot was born! 

International Standard

The common log method might not have been precisely accurate, but it was close enough to give sailors the information they needed for navigation. It was especially innovative for navigation technology in the 17th century. 

While different countries use miles or kilometers, there is not a nautical kilometer measurement. The nautical mile is an international standard measurement used around the globe for maritime navigation. However, there was not always international agreement on what to classify as a knot because some countries used miles while others used kilometers.

The nautical mile was officially established in 1929 by the International Hydrographic Organization using nautical miles. Even so, the UK and US both had been using slightly different measurements at that time. The United States officially adopted the international nautical mile in 1954 and the United Kingdom in 1970.