Knots (kn)

What Is Knots (kn)?

A knot is a unit used to measure speed. It is mainly used for things that move on water or in the air, like ships, boats, and airplanes. One knot means moving one nautical mile in one hour.

People like using knots because the unit works very well with maps that use nautical miles, which are based on the size of the Earth. This makes navigation and planning routes easier and safer.

Definition

A knot is a unit of speed. It tells us how many nautical miles something travels in one hour.

By definition:

• 1 knot = speed of 1 nautical mile per hour
• 1 nautical mile = exactly 1,852 meters

From this, we can convert knots into other common speed units:

• 1 knot ≈ 1.852 kilometers per hour (kmh)
• 1 knot ≈ 1.151 miles per hour (mph)
• 1 knot ≈ 0.514 meters per second (ms)
• 1 knot ≈ 1.688 feet per second (fts)

So if a ship travels at 10 knots, it moves about 18.52 kilometers every hour, or about 11.5 miles every hour.

History / Origin

The name knot comes from an old way sailors measured speed before modern tools existed.

On old sailing ships, sailors used a simple tool called a log line. It was a long rope with knots tied in it at equal distances. One end of the rope had a wooden board that floated behind the ship. As the ship moved forward, the rope played out behind it.

Here is how it worked:

• The sailor threw the wooden board into the water.
• The board slowed down in the water and almost stayed in one place.
• The ship moved forward, pulling the rope through the sailor’s hands.
• Another sailor used a sand glass, like a small hourglass, for a set time.
• They counted how many knots passed through their hands during that time.

The number of knots counted in that fixed time gave the ship’s speed. Over time, this method gave us the word knot for speed at sea.

Today we no longer use ropes and sand glasses, but the name knot stayed and is now a standard unit in many fields.

Symbol & Abbreviation

The most common symbol for knots is:

• kn

You may also see these forms:

• kt for one knot
• kts for more than one knot

All of these mean the same speed unit. Many official documents and charts prefer kn.

Important notes:

• We do not write knots as “nautical miles per hour” even though that is what it means.
• We do not add “ph” after kn. So we write 20 kn, not 20 knph.

Current Use Around the World

Knots are used worldwide, not only in a few countries. They are standard in several important areas.

1. Sea travel and shipping

• All ocean ships and most boats use knots to show speed.
• Sea charts use nautical miles and knots, so calculations are simple.
• Harbors and shipping rules often describe speed limits in knots.

2. Air travel and aviation

• Pilots and air traffic controllers use knots for airspeed.
• Flight plans, approach speeds, and landing speeds are in knots.
• Wind speed for planes is also given in knots.

3. Weather and climate

• Meteorologists and weather services report wind speed in knots, especially near coasts and at sea.
• Storm warnings for ships, such as gale and hurricane warnings, often use knots.

4. Sports and hobbies

• Sailors in races measure their boat speed in knots.
• Yacht owners and powerboat users talk about their cruising speed in knots.
• Some drone and model aircraft users also use knots when working with aviation tools.

Even in countries that mainly use kilometers per hour or miles per hour on roads, knots are still the normal choice for water and air travel.

Example Conversions

Here are some common speeds in knots and what they equal in other units. Values are rounded for easy use.

From knots to kilometers per hour

Use this rule: speed in kmh = speed in knots × 1.852

From knots to miles per hour

Use this rule: speed in mph = speed in knots × 1.151

From knots to meters per second

Use this rule: speed in ms = speed in knots × 0.514

Quick mental conversion tips

• To get kmh from knots, multiply by 2 then subtract about 10 percent. Example 20 kn × 2 = 40, 10 percent of 40 is 4, 40 minus 4 ≈ 36 kmh (real value 37.04).
• To get mph from knots, add about 15 percent. Example 20 kn + 15 percent of 20 (which is 3) ≈ 23 mph.

Related Units

Knots connect closely with several other units used for distance and speed.

• Nautical mile (NM or nmi) distance
  • Distance unit used at sea and in the air.
  • 1 nautical mile = 1,852 meters.
  • Speed in knots tells how many nautical miles are traveled each hour.
• Kilometer per hour (kmh) speed
  • Common road and rail speed unit in most of the world.
  • 1 kn ≈ 1.852 kmh.
• Mile per hour (mph) speed
  • Common road speed unit in the United States and a few other places.
  • 1 kn ≈ 1.151 mph.
• Meter per second (ms) speed
  • Standard scientific unit for speed.
  • Often used in physics and engineering.
  • 1 kn ≈ 0.514 ms.
• Beaufort scale wind force scale
  • Describes wind strength with numbers and words.
  • Behind each Beaufort number there is a range of wind speeds given in knots.
• Mach number high speed ratio
  • Used for very fast aircraft.
  • Often converted from indicated airspeed in knots.

FAQs

Is a knot the same as a nautical mile

No. A nautical mile is a unit of distance. A knot is a unit of speed. One knot means one nautical mile per hour.

Why do sailors and pilots use knots instead of kmh or mph

They use knots because maps for sea and air use nautical miles. When both distance and speed use the same base unit, route planning and safety checks are easier and more exact.

How many kilometers per hour is 1 knot

1 knot is about 1.852 kilometers per hour. You can remember it as a bit less than 2 kmh.

How many miles per hour is 1 knot

1 knot is about 1.15 miles per hour. So 10 knots are about 11.5 mph.

How do I write knots correctly

The common way is to write the number followed by kn. For example 12 kn or 25 kn. In aviation you may also see 12 kt or 25 kts.

Are knots part of the SI system

No. Knots are not an SI unit. The SI unit for speed is the meter per second. However, knots are accepted for use in some technical fields like navigation and aviation.

Can knots be used for cars or bikes

You could use knots for any speed, but people almost never do this on land. For cars and bikes, kmh or mph are more familiar and easier to understand.

Is wind speed always given in knots

Not always. At sea and in aviation, wind is often shown in knots. On TV weather for the general public, wind is usually shown in kmh or mph instead.

How can I quickly compare knots to speeds I know

If you are used to kmh, just think 1 kn is almost 2 kmh. If you are used to mph, think 1 kn is a little more than 1 mph. This gives you a fast rough idea.