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

1 kilometer per hour equals 0.000172603109 miles per second (rounded).

1 kilometer per hour = 0.000172603109 miles per second

How to convert kilometers per hour to miles per second

To convert kilometers per hour to miles per second, multiply the number of kilometers per hour by 0.000172603109. The factor is rounded to 10 significant digits. To go the other way, multiply miles per second by 5,793.6384.

miles per second = kilometers per hour × 0.000172603109

Example: 10 kilometers per hour = 0.00172603109 miles 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

Mile Per Second (mi/s)

US & ImperialCurrent unit

Exactly 1,609.344 m/s. Used for very high speeds.

Spaceflight speeds are where mile per second appears. Escape velocity from Earth's surface is 11.186 km/s, which is about 6.95 mi/s, found by dividing 11,186 m/s by 1,609.344 m. From the Moon the figure is 2.38 km/s, or about 1.48 mi/s, and a low Earth orbit at 7.7 km/s is about 4.8 mi/s, about 69 percent of the Earth escape figure.

The international mile is exactly 1,609.344 m, so one mile per second is exactly that many meters per second, and NIST lists the conversion as exact. It is also 5,793.6 km/h, and one meter per second is therefore about 0.00062 mi/s. NIST cautions that mile per second is not among the units it generally uses in its own publications.

1 mile per second = 1,609.344 meters per second (exactly).

Sources: Wikipedia: Escape velocity; NIST SP 811 Appendix B.8: conversion factors; Wikipedia: Orders of magnitude (speed)

Related conversions

See all speed units.