Why Is It Called knots Instead Of MPH?

Sailing is an ancient, complex and rewarding form of transportation and recreation that has been used for centuries in a variety of contexts, from commercial shipping to leisurely cruising around the globe.

One of the fundamental aspects of sailing is measuring the speed of the vessel, which can be done in a number of units, including knots, miles per hour (MPH), or kilometers per hour (KPH).

But why is it called “knots” instead of MPH? In this article, we will explore the history and origin behind this term, as well as why knots are still preferred by sailors today.

History and Origin

The term “knot” dates back to the 17th century when sailors measured the speed of their ship using a device called a “common log” – a coil of rope with uniformly spaced knots tied in it, attached to a piece of wood shaped like a slice of pie.

This device allowed sailors to measure their speed by counting the number of knots that were pulled out in a given amount of time, then converting that number into distance traveled over time – essentially calculating “miles per hour” as we know it today.

Definition Of Knots

In modern sailing terminology, knots are defined as nautical miles per hour (nmi/hr). A nautical mile is equal to 1.15 standard miles or about 1.85 kilometers, so one knot would be equal to 1 nautical mile per hour or 1.15 mph/1.85 km/h respectively.

Knots vs MPH

So why use knots over mph? The primary reason is because sailors have been using this system for hundreds of years and it has become ingrained in their culture and language – plus they are very familiar with how to calculate speed using knots already which makes them easier to work with than converting from mph or kph each time you need to measure speed on your vessel.

In addition, knots provide an easier way for sailors to compare speeds between different boats since all boats are traveling at a consistent rate regardless if they are on land or sea – something that can’t always be said for mph or kph measurements which can vary depending on sea conditions or other factors like wind speed and direction etc…

Advantages Of Using Knots

In addition to being easy to use and understand for sailors who have been working with knot measurements for centuries, there are also several other advantages associated with using knots over mph or kph measurements:

  • They provide more accurate readings due to their consistency across different vessels,
  • They are easier to convert between different units,
  • They provide an easier way to calculate distances since one knot = one nautical mile,
  • They can be used even when GPS signals are not available,
  • They allow for quick calculations without having to look up conversions every time you need them,
  • They are more precise than mph/kph readings since they take into account variables like wind direction and sea conditions etc…

    Overall, there are many advantages associated with using knot measurements versus mph or kph when measuring speed on your vessel – but what exactly was the device that allowed sailors to measure their speed in knots back in the 17th century? Let’s find out!

The Common Log Device

The common log device was invented by English mathematician Edmund Gunter in 1622 – it consisted of a coil rope with uniformly spaced knots tied into it which was then attached onto a wooden ‘pie’ shaped board known as a ‘common log board’.

This device allowed sailors to measure their speed by counting how many knots were pulled out in a given amount of time – thus giving them an indication as to how many miles they had traveled in that period – essentially calculating ‘miles per hour’ as we know it today!

How The Common Log Device Worked

The common log device worked by attaching one end of the rope (which had evenly spaced knots tied into it) onto the ‘common log board’ while leaving some slack so that when pulled back on itself, each knot would line up perfectly with its corresponding slot on the board – this created an even spacing between each knot which made them easier to count when measuring speed over time! When sailing at sea, sailors would pull back on this rope until one full knot had passed through its corresponding slot on the board – this indicated that one nautical mile had been traveled within one hour’s time (hence ‘miles per hour’). This process could then be repeated until desired results were achieved!

The Benefits Of Using The Common Log Device

Using this method was beneficial not only because it provided accurate measurements but also because it could be done quickly without having to rely on more complex calculations such as those required for calculating winds/current speeds etc…

Additionally, due its inherent simplicity this method could easily be replicated across different vessels allowing for faster comparisons between ships when needed!

How Knots Are Calculated Nowadays

Today most vessels will use either GPS systems or radar systems (or both) in order to determine their current speed – however some still prefer using traditional methods such as those utilized by Gunter’s common log device centuries ago! When using these methods however there may be slight discrepancies due things such as wind direction/speed etc… so if accuracy is paramount then GPS/radar systems should always be used first!

Popular Examples Of Measuring Speed With Knots

Knot measurements remain popular among many experienced sailors who prefer its simplicity and accuracy over other more modern methods such as GPS systems etc… Some popular examples include:

  • Racing yachts: Sailors involved in racing yachts often use knot measurements due its precision compared other more generalised forms such as mph/kph readings,
  • Commercial shipping: Large commercial ships often rely on knot measurements due its accuracy and ability for quick comparisons between vessels,
  • Fishing boats: Fishing boats often use knotted ropes when measuring distances travelled over time – again due its accuracy & ease compared other methods,
  • Military vessels: Military vessels often rely heavily on knot measurements when navigating hostile waters where GPS signals may not always be available etc…

    Ultimately though its up individual preference whether one prefers using knot measurements over other forms such as mph/kph etc… however most experienced sailors will agree that knot readings remain far superior when accuracy & consistency is paramount!


    In conclusion we have established that ‘knots’ refers specifically nautical miles per hour (nmi/hr) rather than miles/kilometers per hour like most people assume – this term originated back during 17th century where sailor used devices known as ‘common logs’ which allowed them accurately measure distances travelled within given periods time without relying complex calculations like those required winds/current speeds etc… Today most vessels will either use GPS systems radar systems (or both) order determine current speed however some still prefer utilising traditional methods used centuries ago! Ultimately though preference whether one prefers using knot measurement other forms such MPH/KPH etc… but experienced sailor agree remain far superior accuracy & consistency paramount!

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