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 centimetre per second?

Centimetre per second is a unit of speed used in low-velocity applications such as biological locomotion studies, microfluidics research, and slow-moving mechanical systems.

Real-world uses

Centimetres per second is used in the CGS system for fluid flow rates, sedimentation velocities in geology, and blood flow measurements in medical Doppler ultrasound. Glacier movement and tectonic plate motion are sometimes expressed in cm/s or cm/year.

History

Centimetres per second was the standard velocity unit in the CGS (centimetre-gram-second) system, widely used in physics until the mid-20th century. While SI uses m/s, cm/s persists in certain scientific fields, particularly fluid mechanics and geophysics.

Common mistakes

Confusing cm/s with m/s by forgetting the factor-of-100 difference. Also, assuming cm/s is too small for practical use—blood flow in major arteries is typically 10–40 cm/s, which is a very practical range.

When is this conversion used?

Converting kilometre per second to centimetre 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 = 100,000 centimetre per second

1 centimetre per second = 0.01 metre per second

How to convert kilometre per second to centimetre per second

To convert kilometre per second to centimetre per second, multiply the value by 100,000.

To convert centimetre per second back to kilometre per second, multiply by 0.00001.

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 centimetre per second

kilometre per second	centimetre per second
0.1	10,000
0.5	50,000
1	100,000
2	200,000
5	500,000
10	1,000,000
25	2,500,000
50	5,000,000
100	10,000,000
250	25,000,000
500	50,000,000
1,000	100,000,000

Common values

	kilometre per second	centimetre per second
Walking speed	0.0014 kilometre per second	140 centimetre per second
City speed limit	0.0139 kilometre per second	1,390 centimetre per second
Highway driving	0.0313 kilometre per second	3,130 centimetre per second
Commercial aircraft	0.25 kilometre per second	25,000 centimetre per second
Speed of sound (sea level)	0.34029 kilometre per second	34,029 centimetre per second

Available Speed units

More kilometre per second conversions

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