Speed Converter
Instantly convert between km/h, mph, m/s, knots, ft/s, plus Mach and the speed of light (c).
km/h
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FAQ
Why do aviators use knots (kn)?
Knots are nautical miles per hour. Because navigation uses nautical miles (1 nmi = 1,852 m), knots line up with charts and air/sea distances.
Is an mph exactly defined?
Yes. 1 mph = 1 statute mile per hour and 1 mile is exactly 1,609.344 m, so 1 mph ≈ 0.44704 m/s.
What is Mach?
Mach is speed relative to the local speed of sound. We use ISA sea-level 15 °C (≈340.29 m/s) as a reference; real Mach varies with temperature/altitude.
What does “c” mean?
c is the speed of light in vacuum (exactly 299,792,458 m/s). Useful for scientific comparisons—not your daily commute 😉.