Kilometers Per Hour to Kilometers Per Second (km/h to km/s)

1 kilometer per hour equals 0.0002777777778 kilometers per second (rounded).

1 kilometer per hour = 0.0002777777778 kilometers per second

How to convert kilometers per hour to kilometers per second

To convert kilometers per hour to kilometers per second, multiply the number of kilometers per hour by 0.0002777777778. The factor is rounded to 10 significant digits. To go the other way, multiply kilometers per second by 3,600.

kilometers per second = kilometers per hour × 0.0002777777778

Example: 10 kilometers per hour = 0.002777777778 kilometers per second.

About these units

Kilometer Per Hour (km/h)

Metric (SI)Current unit

The standard unit for road speeds in most countries: 1 km/h is about 0.2778 m/s.

Myriameters per hour came first, at least in French. Although the meter was defined in 1799, speeds were initially quoted using the myriameter of 10,000 meters, and the phrase myriamètres par heure appears in 1802. The Dutch adopted the kilometer in 1817 under the name mijl. English abbreviations only appeared in the late nineteenth century, and many competing forms followed, from k. p. h. in 1889 to KMPH in 1940. Reuters and The Economist still prefer kph.

SI treats km/h as a unit symbol, not an abbreviation, and it is the generally preferred form. The European Union required SI usage in 1972, and a 1975 directive requires km/h on speedometers in all languages. In the United States a 1988 NHTSA rule allowed km/h on speedometers. Exactly 3.6 km/h make 1 m/s, one mile per hour is exactly 1.609344 km/h, and one knot is exactly 1.852 km/h. Road signs and speed limits in most of the world use it.

1 kilometer per hour = 0.2777777778 meters per second (approximately).

Sources: Wikipedia: Kilometres per hour; NIST Guide to the SI, Appendix B.8: conversion factors

Kilometer Per Second (km/s)

ScientificCurrent unit

1,000 m/s. Used for orbital velocities; low Earth orbit is about 7.7 km/s.

Orbital mechanics is where kilometers per second become the everyday scale. A satellite in a circular low Earth orbit between 200 and 2,000 km altitude travels at 7.7 to 6.9 km/s, and the International Space Station and typical low orbit satellites move at about 7.7 km/s, which is 27,700 km/h. Earth itself circles the Sun at an average of about 29.8 km/s, roughly 3.9 times that low orbit speed, since 29.8 divided by 7.7 is 3.87.

The unit also suits escape velocities, such as 11.186 km/s from the surface of Earth and 2.38 km/s from the Moon, and the speed of sound in water, about 1.5 km/s. It is a thousand times the SI base speed of 1 m/s, so quoting orbital motion in meters per second would mean long strings of digits.

1 kilometer per second = 1,000 meters per second (exactly).

Sources: Wikipedia: Orbital speed; Wikipedia: Escape velocity; Wikipedia: Orders of magnitude (speed)

Related conversions

See all speed units.