Speed Converter

Multiply km/h by 0.621371. Example: 100 km/h = 62.14 mph. This matters for reading foreign speed limits correctly — being 50 km/h over a limit is the same excess speed as being about 31 mph over, even though the mph number looks smaller.

Multiply mph by 1.60934. Example: 60 mph = 96.56 km/h. Useful for interpreting speed limits abroad or reading a rental car's metric speedometer.

Mach is a speed expressed as a ratio to the local speed of sound, which depends on air temperature and altitude — it is not a fixed speed. This converter uses the standard sea-level, 15°C reference: Mach 1 = 340.29 m/s = 1,225 km/h = 761 mph. Real aircraft cruising at altitude, where sound travels slower, correspond to a different actual speed for the same Mach number.

1 knot = 1 nautical mile per hour = 1.852 km/h = 1.15078 mph. It's the standard unit in aviation and marine navigation (ICAO convention) — for example, a cruising airliner at 450 knots is about 833 km/h.

The underlying factors follow standard definitions (1 knot = 1.852 km/h exactly), so results are accurate for general reference and planning. For flight data recorders, official accident investigations, or other safety-critical or legal use, always use the official source data rather than a third-party converter.