Speed - Units

Units

Units of speed include:

  • meters per second (symbol m s−1 or m/s), the SI derived unit;
  • kilometers per hour (symbol km/h);
  • miles per hour (symbol mi/h or mph);
  • knots (nautical miles per hour, symbol kn or kt);
  • feet per second (symbol fps or ft/s);
  • Mach number (dimensionless), speed divided by the speed of sound;
  • in natural units (dimensionless), speed divided by the speed of light in vacuum (symbol c = 299,792,458 m/s).
Conversions between common units of speed
m/s km/h mph knot ft/s
1 m/s = 1 3.6 2.236936 1.943844 3.280840
1 km/h = 0.277778 1 0.621371 0.539957 0.911344
1 mph = 0.44704 1.609344 1 0.868976 1.466667
1 knot = 0.514444 1.852 1.150779 1 1.687810
1 ft/s = 0.3048 1.09728 0.681818 0.592484 1

(Values in bold face are exact.)

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