How Fast is a Knot and What Does it Mean?

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Just as your airline pilot offers useful snippets of information such as cruising altitude and speed, cruise ship captains love to regale passengers with similar insights.

In the exciting world of marine navigation, it’s fair to say that most of us don’t have a handle on all the terminology. For the most part, this doesn’t really matter – until we set foot on the deck of a cruise ship.

Suddenly we want to understand how fast is a knot, and what is a nautical mile anyway? If these nautical terms have always puzzled you, then read on. We have explored them in detail below.

Nautical Navigation Unpacked

You may rightly question why distance and speed are measured differently at sea compared to land. This is an excellent question and forms the basis of all nautical navigational reasoning. 

At the very root of it, land and sea travel differ in one key area: the sea has no landmarks. At no point can we turn left onto 51st Street and continue until we get to the T-junction.

Cruise Navigation
Cruise Navigation (Photo Credit: Solomakha / Shutterstock)

This means that tracking our position on the water relies on a different map, that being the latitude and longitude coordinates of the earth. These measurements are ideal for long-distance travel and take into account the earth’s curvature when establishing an accurate position. 

So, to fully understand how fast a knot is, we need a bit more information on exactly how ocean travel is measured. The basics are as follows:

  • A statute mile is another name for a land-measured mile
  • A nautical mile is a distance measurement equating to 1.1506 statute miles
  • One nautical mile equals one minute of latitude

How Fast Is a Knot?

Now that we have a grasp on how sea-faring folk measure distance, we can better understand the answer to the question, “How fast is a knot?”

A knot is a measure of speed and equates to one nautical mile per hour. (Approximately 1.15 statute miles.) Therefore the ratio of knots vs. mph is 1:1.15.

Why, though, would sailors use the term “knot” when referring to speed? The answer lies in history, around the 17th century to be exact. Minus the modern tech that we enjoy today, sailors used a “common log.” This beautifully simple solution consisted of a rope with knots tied at regular intervals and connected to a piece of wood. 

Dry red floats with a rope for speed measurement
Dry red floats with a rope for speed measurement (Photo Credit: Tatyana Blinova / Shutterstock)

The rope was tossed overboard behind the vessel, and the able seamen would then flip an hourglass to measure a specific amount of time. Once the time was up, they would pull up the rope and count the knots between the wood and the boat. This gave them a measurement of speed hence the term knots or knot speed.

It may not have been the most accurate measurement, but it was enough to allow ancient mariners to navigate with sufficient accuracy to get to where they were going. 

Summing Up

We answer the FAQs on this fascinating topic below.

What is a knot?

A knot is a measurement of speed equal to one nautical mile per hour.

How fast is a nautical mph?

One nautical mile per hour equates to 1.15 land miles per hour.

How do I convert knots to mph?

Converting knots to mph is a simple multiplication of mph by 1.15

How fast is 20 knots?

Using our working above you can determine that 20 knots equates to 23 mph, which is the average speed of a cruise ship.

See You Onboard!

In this article, we hope that we provided you with the necessary details to better understand what your ship captain is telling you during your next cruise.

Also Read: How Fast Do Cruise Ships Go?

So, when he tells you that you’re traveling at 21kn and your fellow passengers look at you and ask, “How fast is a knot?” you can speak with conviction. And then, possibly deep dive into unpacking “How fast is 21 knots?”

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