What is knot?
A knot is a unit of speed equal to one nautical mile per hour, approximately 1.852 km/h. It is the international standard for maritime navigation, aviation, and meteorological wind speed reporting.
Real-world uses
Knots are the universal speed unit in maritime navigation and aviation worldwide, regardless of whether a country uses metric or imperial. Ship speeds, ocean currents, wind speed in aviation weather (METAR) reports, and jet stream velocities are all given in knots.
History
The knot originates from the 17th-century practice of measuring ship speed by throwing a log overboard attached to a rope with knots tied at regular intervals. Sailors counted how many knots paid out in a fixed time (measured by a sandglass).
Common mistakes
Saying "knots per hour"—a knot already means nautical miles per hour, so adding "per hour" is redundant and incorrect. Also, confusing knots with km/h: 1 knot ≈ 1.852 km/h.
What is kilometre per second?
Kilometre per second is a unit of speed equal to 1,000 metres per second. It is used in astrophysics, rocket propulsion, and the measurement of planetary and cosmic velocities.
Real-world uses
Kilometres per second is used in astronomy and astrophysics for orbital velocities, galaxy recession speeds, and asteroid approach velocities. Earth orbits the Sun at about 29.78 km/s, and escape velocity from Earth is about 11.2 km/s.
History
Kilometres per second became a standard unit in celestial mechanics and astrophysics during the 20th century. It provides convenient numbers for solar system velocities, while larger cosmic speeds are often expressed as fractions of the speed of light.
Common mistakes
Forgetting the enormous scale—1 km/s = 3,600 km/h. A common error is treating km/s figures as if they were km/h. Also, confusing orbital speed with escape velocity, which are related but different concepts.
When is this conversion used?
Converting between knot and kilometre per second is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.
Worked examples
1 knot = 0.00051444 kilometre per second
1 kilometre per second = 1,000 metre per second
How to convert knot to kilometre per second
To convert knot to kilometre per second, multiply the value by 0.00051444.
To convert kilometre per second back to knot, multiply by 1,943.84449261.
Measurement standards
The SI unit of speed is metres per second (m/s), a derived unit requiring no independent definition. The knot is defined as exactly one nautical mile (1,852 metres) per hour and is sanctioned for maritime and aeronautical navigation by the International Civil Aviation Organization.
Did you know?
The fastest human-made object is the Parker Solar Probe, which reached 635,266 km/h (about 176 km/s) in 2024 during a close pass of the Sun — fast enough to travel from New York to Tokyo in under a minute.
Quick reference: knot to kilometre per second
| knot | kilometre per second |
|---|---|
| 0.1 | 0.00005144 |
| 0.5 | 0.00025722 |
| 1 | 0.00051444 |
| 2 | 0.00102889 |
| 5 | 0.00257222 |
| 10 | 0.00514444 |
| 25 | 0.01286111 |
| 50 | 0.02572222 |
| 100 | 0.05144444 |
| 250 | 0.12861111 |
| 500 | 0.25722222 |
| 1,000 | 0.51444444 |
Common values
| knot | kilometre per second | |
|---|---|---|
| Walking speed | 2.72138229 knot | 0.0014 kilometre per second |
| City speed limit | 27.01943845 knot | 0.0139 kilometre per second |
| Highway driving | 60.84233262 knot | 0.0313 kilometre per second |
| Commercial aircraft | 485.96112315 knot | 0.25 kilometre per second |
| Speed of sound (sea level) | 661.47084239 knot | 0.34029 kilometre per second |
Available Speed units
More knot conversions
- Convert knot to metre per second
- Convert knot to kilometre per hour
- Convert knot to mile per hour
- Convert knot to foot per second
- Convert knot to metre per minute
- Convert knot to kilometre per second
- Convert knot to mach (approx at sea level)
- Convert knot to centimetre per second
- Convert knot to mile per minute
Assumption: Mach uses an approximate sea-level reference (about 340.29 m/s).