“We’re reaching 18 knots with headwind...” These words from the captain over the ship’s PA often leave passengers puzzled. Why not just speak in kilometers per hour? Is it just another sailor’s term meant to impress newcomers? Actually, no. There’s something far more interesting behind it.
Contents
- From rope and wood to GPS: a story of nautical ingenuity
- Why knots fit perfectly with maritime maps
- Why kilometers work well on land but not at sea
- A global standard firmly established
- Fun facts about cruise ship speeds
- Efficiency versus speed
- The legendary SS United States
- Knots beyond the sea
- International terminology
- FAQs about knots (speed unit)
The Fascinating History of Knots
Knots have a curious story. They don’t survive just because sailors like sticking to tradition (though they do). They remain because knots are remarkably practical — a surprise to many when they first discover the reason.
Recently, a reader asked us about this very topic, so today we want to explain this fascinating nautical curiosity—a concept that blends tradition, practicality, and global geography.
What You Should Know:
- One knot equals one nautical mile per hour
- A nautical mile equals exactly one minute of latitude
- This relationship greatly simplifies navigation
- Knots are universal in global navigation
From Rope and Wood to GPS: A Story of Nautical Ingenuity
Have you ever wondered how ancient sailors measured a ship’s speed without GPS or digital instruments? The method is quite curious and explains why we still talk about “knots” today.
Back in the 16th century, sailors tossed a piece of wood attached to a rope off the stern. This rope literally had knots tied at precise intervals. As the ship advanced, they let the rope pay out for a fixed time measured by an hourglass. The number of knots passing through their hands indicated the ship’s speed.
Primitive? Yes. But surprisingly effective.
What’s truly fascinating is that this system gave its name to the unit we still use today on the most sophisticated ship bridges. From those early ropes with knots to modern GPS, the word remains.
Why Knots Fit Perfectly with Nautical Maps
Here lies the real reason knots have endured: the nautical mile — exactly what you travel in an hour at one knot — is no arbitrary measurement. It equals exactly one minute of arc of latitude.
This simplifies navigation dramatically. Sailing at 10 knots for 6 hours means you’ve covered 60 nautical miles — exactly one degree of latitude on any nautical chart.
Imagine how practical this is for a navigator: you can measure distances directly on a chart’s scale with no calculator or complex conversions. Out in the ocean, perhaps in bad weather, this simplicity can make all the difference.
Ultimately, it boils down to this: knots and nautical miles aren’t a whim. They are part of a system where speed, time, and distance are directly linked to the lines dividing our planet.
Kilometers: Practical on Land, Problematic at Sea
The kilometer, while very useful on land, has no natural relationship to geographic coordinates. It’s an arbitrary unit based on the metric decimal system.
For maritime professionals, using kilometers means constantly doing mathematical conversions when working with navigation charts and coordinates. In situations where speed and precision matter, this added complexity would pose real problems.
A Globally Established Standard
This isn’t just a matter of preferences. The entire global navigation infrastructure is based on nautical miles and knots:
- Nautical charts worldwide
- International maritime traffic control systems
- Communication protocols between ships
- International maritime laws and regulations
- Training for navigators worldwide
Changing this global system would require a massive coordinated effort, with astronomical costs and questionable benefits.
Fun Facts About Cruise Ship Speeds
Efficiency Versus Speed
Have you ever wondered why cruise ships don’t go faster? Most cruise ships sail leisurely at speeds between 18 and 22 knots. Pure economics — nothing more.
On board the Symphony of the Seas, an engineer explained to us that fuel consumption rises drastically with small speed increases.
Cruise lines juggle sailing time, fuel savings, and pressure to pollute less. With today's fuel prices, every extra knot costs thousands of euros per day.
The Legendary SS United States
The king of speed at sea remains a veteran. The SS United States, an ocean liner from 1952, holds the commercial speed record at 38.3 knots (about 71 km/h).
Interestingly, no modern cruise ship has seriously tried to beat this record in seven decades. The old United States was also designed for military transport in wartime, explaining its powerful turbines.
Today, cruise ships focus on efficiency, not speed. They’re floating hotels, not sea racers (except the last ocean liner still active, the Queen Mary 2).
Knots Beyond the Sea
Did you know airplanes also measure speed in knots? If you check your in-flight monitor next time, you’ll see something like 480 knots, not kilometers per hour.
The reason is the same: when calculating routes based on terrestrial coordinates, knots and nautical miles simplify navigation. A fascinating link between ships and planes that most passengers overlook.
International Terminology
A linguistic detail: the term “knot” literally refers to a knot in almost every language. “Knot” in English, “nœud” in French, “nodo” in Italian… all preserve the reference to those knotted ropes sailors used centuries ago.
Modern measurement units usually have more abstract names, but this one reminds us of its origin every time we mention it.
Frequently Asked Questions About Knots
How to Quickly Convert Knots to Kilometers per Hour?
“How many km/h is that?” This is probably the most common question when talking about knots. The exact formula is to multiply by 1.852, but who does that mentally?
Here’s a sailor’s trick: multiply by 2 and subtract 10%. For example, 20 knots × 2 = 40, minus 4 = 36 km/h. The actual value is 37 km/h, but this quick estimate works perfectly for a rough idea.
Why Do Marine and Land GPS Devices Use Different Units?
GPS devices are optimized for their environments. Your car GPS shows km/h because roads and land maps use that metric. Marine GPS units show knots because maritime maps and navigation are based on nautical miles.
It’s fascinating that the same device changes how it displays measurements depending on context — true adaptation to the medium.
Do River Cruises Also Use Knots?
Generally, yes. However, on some European rivers, you may see speed shown both in knots and km/h, especially in passenger information to help understanding.
Will Nautical Navigation Ever Switch to the Metric System?
It’s highly unlikely. The current system works perfectly, is universally accepted, and deeply integrated into all nautical infrastructure. Changing it would cause more problems than benefits.
A Tradition with a Practical Purpose
Knots are one of those cases where tradition lasts not because of resistance to change, but because it remains the optimal solution.
Next time you hear “we’re sailing at 20 knots,” you’ll know it’s not maritime jargon or an old relic.
It’s a unit perfectly adapted to navigation needs, an elegant system connecting speed directly with our planet’s geography.
Will Knots Remain the Maritime Speed Standard?
This fast-paced world raises the question: will we ever see a shift towards metric units in maritime navigation?
Based on conversations with many maritime professionals over the years, the answer is a resounding “no.”
The practicality of this system and its universal integration make any change more problematic than beneficial.
Most likely, we will continue seeing this duality: speed in knots for professionals and often a km/h conversion in passenger information to aid understanding.
What we can say for sure is that speed in knots not only connects us to maritime tradition, but also represents a mathematically elegant system perfectly tuned for navigation needs.
Want to learn more about nautical terms and how they affect your onboard experience? Share your questions in the comments and we’ll answer them in future articles.
The next time you’re on a cruise and the captain mentions knots, you’ll know exactly what they mean and why this ancient measure remains vital in the 21st century.
Your Opinion Matters:
Had you heard about knots before? Do you find this connection between tradition and practicality in the maritime world interesting?
We’d love to hear if you’ve had any experiences related to this during your cruises. Maybe you heard the captain mention speed in knots and wondered why, or perhaps you have other questions about nautical terms you’d like us to explain.
Share your thoughts in the comments. Your questions help us create content that truly interests cruise lovers.