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Speed (velocity)
Speed (velocity) units converter - converts units between metric (kilometres per hour, meters per second and many more), british-american (miles per hour, foot per second and many more), nautical (knots) and some other (machs, speed of light etc.)
Some facts
  • Velocity is a vector size.
  • It specifies the change of the position vector in time. The concept of velocity was formalized with the development of calculus. Since then, the velocity is defined as the position vector derivative with time i.e. v = dr / dt, where v is a velocity vector r position vector and t is a time.
  • In common parlance - when we use the word speed - we normally refer to the scalar size, representing the value of the velocity vector (its "length").
  • The velocity by definition only applies to singl point in time. Sometimes, in order to emphasize this fact (and rule out a possible confusion with the average speed) it is called instantaneous velocity.
  • There is also concept of average velocity, which is ratio of distance to time, in which this distance has been traveled.
  • Average velocity is sometimes colloquially called speed, but it is not a phrase used by physicists.
  • The basic unit of velocity in the SI system is m/s (meters per second).
  • According to Einstein's theory of relativity the highest attainable speed in nature is the speed of light amounting to 299 792 458 m/s.

    • The speed of light constant exists in many physical formulas e.g. equation desribing the equivalence of energy and mass E=mc2.
    • Einstein's special theory of relativity gives a more general sense of the speed of light as limit velocity of energy transport (or otherwise velocity of impact) in the universe..
    • The light is electromagnetic wave with the frequency that is visible to the human eye. However, the speed of light concerns to all of electromagnetic waves and does not depend on their frequency. This means that for example radio or wifi signals are transmited with the speed of light.

  • Other common velocity constants are for example:

    • First cosmic velocity - the smallest horizontal velocity to be given to the body relative to the celestial body attracts them to the body is moved along a closed orbit. In other words, it is the speed needed to became a satellite.
    • Second cosmic velocity - the velocity needed to "break free" from the gravitational attraction of the given orb (for example Earth)..
    • Third cosmic velocity - the initial velocity which a body has to have to leave the Solar System.
    • Fourth cosmic velocity - the initial velocity needed to leave the Milky Way.
How to convert?
  • Enter the number to field "value" - enter the NUMBER only, no other words, symbols or unit names. You can use dot (.) or comma (,) to enter fractions.
    • 1000000
    • 123,23
    • 999.99999
  • Find and select your starting unit in field "unit". Some unit calculators have huge number of different units to select from - it's just how complicated our world is...
  • And... you got the result in the table below. You'll find several results for many different units - we show you all results we know at once. Just find the one you're looking for.
value: unit: decimals:


kilometres per hour [km/h]
kilometres per minute [km/min]
kilometres per second [km/s]
metres per hour [m/h]
metres per minute [m/min]
metres per second [m/s]


miles per hour [mph]
miles per minute
miles per second [mps]
foot per hour [fph]
foot per minute [fpm]
foot per second [fps]
inch per hour [iph]
inch per minute [ipm]
inch per second [ips]
furlong per fortnight


speed of light in vacuum [c]
speed of sound in air
mach [M]
knot [kn]
velocity · speed

Tags to Polish version:
predkosc · szybkosc