Convert Kilometer/Second (km/s) to Mile/Hour (mi/h) instantly.
About these units
Kilometer/Second (km/s)
A kilometer per second represents a very high speed—1,000 meters every second—and is particularly important in astronomy, planetary science, and astrophysics. Orbital velocities around planets, escape velocities, solar winds, and the motion of stars relative to each other are commonly measured in km/s. This scale captures speeds far beyond terrestrial transportation. For example, Earth orbits the Sun at roughly 30 km/s, and meteoroids entering Earth's atmosphere may arrive at speeds between 11 and 72 km/s. km/s is a natural step up from m/s when describing the motion of celestial bodies.
Mile/Hour (mi/h)
The mile per hour represents the number of miles traveled in one hour and is commonly used in the United States, the UK (in road contexts), and several other countries with legacy imperial systems. mph is deeply woven into cultural habits: driver training, speed limits, vehicular performance, and even athletic achievements are often expressed in miles per hour. In science and engineering, however, mph is rarely used because the mile and hour are not SI units. Still, mph retains strong emotional and historical associations—for example, the significance of a car "breaking 200 mph" or the legendary "88 mph" in popular culture. It persists because measurement units often survive long after their historical origins fade.