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.

What is metre per second?

Metre per second is the SI unit of speed. It is used in physics, engineering, and scientific contexts to express velocity, and serves as the reference unit for all speed calculations in this converter.

Real-world uses

Metres per second is the SI unit of speed used in physics, engineering, and scientific research. Wind speed in meteorological data, projectile velocities, and fluid flow rates are expressed in m/s. The speed of sound at sea level is approximately 343 m/s.

History

As an SI derived unit, metres per second became the standard scientific speed unit with the adoption of the SI system in 1960. It naturally combines the base units of length (metre) and time (second).

Common mistakes

Forgetting to convert from km/h—divide by 3.6, not by 3.0 or 60. Also, confusing velocity (vector with direction) with speed (scalar magnitude), both expressed in m/s but with different physical meanings.

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.

Worked examples

1 kilometre per second = 1,000 metre per second

1 metre per second = 1 metre per second

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.

To convert metre per second back to kilometre per second, multiply by 0.001.

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: kilometre per second to metre per second

kilometre per second	metre 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

	kilometre per second	metre per second
Walking speed	0.0014 kilometre per second	1.4 metre per second
City speed limit	0.0139 kilometre per second	13.9 metre per second
Highway driving	0.0313 kilometre per second	31.3 metre per second
Commercial aircraft	0.25 kilometre per second	250 metre per second
Speed of sound (sea level)	0.34029 kilometre per second	340.29 metre per second

Available Speed units

More kilometre per second conversions

Assumption: Mach uses an approximate sea-level reference (about 340.29 m/s).