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Speed Units Explained
Also searched as: speed converter online free | mph to kmh converter | kilometers per hour to mph | knots to mph converter Optimized for US users with American units and terminology.
The meter per second (m/s) is the SI unit of speed. A knot is one nautical mile per hour (1.852 km/h), used in aviation and maritime navigation. Mach 1 is the speed of sound at sea level — about 340.29 m/s (1,235 km/h) at 15°C. The speed of light in vacuum is exactly 299,792,458 m/s (approximately 1.08 billion km/h).
Mach number is the ratio of an object's speed to the speed of sound in the surrounding medium. Mach 1 at sea level at 15°C is about 340.29 m/s (1,235 km/h or 767 mph). Mach 2 is twice the speed of sound. The exact Mach speed changes with altitude and temperature — at 30,000 feet, Mach 1 is only about 1,062 km/h.
One knot equals one nautical mile per hour, which is 1.852 km/h or 1.15078 mph. Knots are the standard speed unit in aviation and maritime navigation. A nautical mile (1,852 meters) is based on one minute of arc of latitude, making it natural for navigation.