Miles Per Hour to Kilometers Per Second (mph to km/s)

1 mile per hour equals 0.00044704 kilometers per second exactly.

1 mile per hour = 0.00044704 kilometers per second

How to convert miles per hour to kilometers per second

To convert miles per hour to kilometers per second, multiply the number of miles per hour by 0.00044704. This factor is exact. To go the other way, multiply kilometers per second by 2,236.936292 (rounded).

kilometers per second = miles per hour × 0.00044704

Example: 10 miles per hour = 0.0044704 kilometers per second.

About these units

Mile Per Hour (mph)

US & ImperialCurrent unit

Exactly 0.44704 m/s. The unit for road speeds in the US, UK and a few other countries.

Early British motoring law is the best window into this unit. The 1861 Locomotive Act set a limit of 10 mph for light locomotives. The 1865 Red Flag Act cut it to 4 mph in the country and 2 mph in towns, with a person walking ahead with a flag. The Locomotives on Highways Act of 1896 raised it to 14 mph, and the Motor Car Act of 1903 to 20 mph. In 1931 all limits for cars were abolished, and 30 mph in built-up areas returned in 1935.

The mile per hour combines the mile, set at 5,280 feet in Elizabeth I's reign, with the hour, and it equals exactly 0.44704 m/s or 1.609344 km/h. The United Kingdom and United States use it on roads, along with several smaller countries, mostly territories or former territories of those two, and the US, Canada and Ireland use it for rail. Sports such as cricket, tennis and baseball quote ball speeds in it. Aviation and shipping prefer knots, about 0.869 of one mph each.

1 mile per hour = 0.44704 meters per second (exactly).

Sources: Wikipedia: Miles per hour; Wikipedia: Speed limits in the United Kingdom; Wikipedia: Mile

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.