kilometre per second (km/s)
1 kilometre per second = 1,000 metres per second
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.
Notes: High speed
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 kilometre per second to metre per second is useful in the speed domain when comparing values across different measurement standards or applying formulas that require a specific unit.
How to convert kilometre per second to metre per second
To convert kilometre per second to metre per second, multiply the value by 1,000.
Conversion formula (from base unit)
x * 1000.0
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.
| kilometres per second | metres per second |
|---|---|
| 0.1 | 100 |
| 0.5 | 500 |
| 1 | 1,000 |
| 2 | 2,000 |
| 5 | 5,000 |
| 10 | 10,000 |
| 25 | 25,000 |
| 50 | 50,000 |
| 100 | 100,000 |
| 250 | 250,000 |
| 500 | 500,000 |
| 1,000 | 1,000,000 |
Common values
| kilometres per second | metres per second | |
|---|---|---|
| Walking speed | 0.0014 kilometres per second | 1.4 metres per second |
| City speed limit | 0.0139 kilometres per second | 13.9 metres per second |
| Highway driving | 0.0313 kilometres per second | 31.3 metres per second |
| Commercial aircraft | 0.25 kilometres per second | 250 metres per second |
| Speed of sound (sea level) | 0.34029 kilometres per second | 340.29 metres per second |
Full kilometre per second conversion table
| Unit | Value | Factor |
|---|---|---|
| metre per second | 1 km/s = 1,000 m/s | × 1,000 |
| kilometre per hour | 1 km/s = 3,599.99999971 km/h | × 3,599.99999971 |
| mile per hour | 1 km/s = 2,236.93629205 mph | × 2,236.93629205 |
| knot | 1 km/s = 1,943.84449261 kn | × 1,943.84449261 |
| foot per second | 1 km/s = 3,280.83989501 ft/s | × 3,280.83989501 |
| metre per minute | 1 km/s = 60,000 m/min | × 60,000 |
| mach (approx at sea level) | 1 km/s = 2.93866996 Ma | × 2.93866996 |
| centimetre per second | 1 km/s = 100,000 cm/s | × 100,000 |
| mile per minute | 1 km/s = 37.28227153 mi/min | × 37.28227153 |