Speed or Velocity Conversion Calculator

Select Units to Convert: From:   To: centimeter per minute (cm/min) centimeter per second (cm/s) foot per hour (ft/h) foot per minute (ft/min) foot per second (ft/s) inch per minute (in/min) inch per second (in/s) kilometer per hour (km/h or kph) kilometer per second (km/s) knot (nautical mi/h) (kn) knot (UK) (kn) meter per hour (m/h) meter per minute (m/min) meter per second (m/s) mile per hour (mi/h or mph) mile per minute (mi/min) mile per second (mi/s) speed-of-light (vacuum) (c) yard per hour (yd/h) yard per minute (yd/min) yard per second (yd/s)   centimeter per minute (cm/min) centimeter per second (cm/s) foot per hour (ft/h) foot per minute (ft/min) foot per second (ft/s) inch per minute (in/min) inch per second (in/s) kilometer per hour (km/h) kilometer per second (km/s) knot (nautical mi/h) (kn) knot (UK) (kn) meter per hour (m/h) meter per minute (m/min) meter per second (m/s) mile per hour (mi/h) mile per minute (mi/min) mile per second (mi/s) speed-of-light (vacuum) (c) yard per hour (yd/h) yard per minute (yd/min) yard per second (yd/s) Enter Value to Convert:     | Share

What are Speed and Velocity

Speed is the rate of change in position of a moving quanity, without factoring direction into the equation. Walk forwards or backwards at 2 meters per second, and your speed is just that: 2 m/s. Velocity is speed in the context of direction. Say you were walking backwards again: your velocity would be negative 2 m/s, although your speed would still be positive.

For most science applications, the SI unit for speed and velocity is meters per second (m/s), although kliometers per hour (km/h) are sometimes used when measuring the speed of vehicles. The English system usually expresses speed as miles per hour (mph) or sometimes feet per second (ft/s), while marine vessels typically use knots, or nautical miles per hour.

How to Convert Units of Speed

Conversions are performed by using a conversion factor. By knowing the conversion factor, converting between units can become a simple multiplication problem:

S * C = E

Where S is our starting value, C is our conversion factor, and E is our end converted result.

To simply convert from any unit into meters per second, for example, from 5 mph, just multiply by the conversion value in the right column in the table below.

5 mph * 0.44704 [ (m/s) / (mph) ] = 2.2352 m/s

To convert from m/s into units in the left column divide by the value in the right column or, multiply by the reciprocal, 1/x.

2.2352 (m/s) / 0.44704  [ (m/s) / (mph) ] = 5 mph

To convert among any units in the left column, say from A to B, you can multiply by the factor for A to convert A into meters per second then divide by the factor for B to convert out of Pascals.  Or, you can find the single factor you need by dividing the A factor by the B factor.

For example, to convert from miles per hour to kilometers per hour inch you would multiply by 0.44704 then divide by 0.2777778.  Or, multiply by 0.44704/0.27777778 = 1.6093439. So, to convert directly from mph to km/h (kph), you multiply by 1.6093439.

References/ Further Reading

The National Institute of Standards and Technology (NIST) - The NIST Guide for the use of the International System of Units - Appendix B, subsections B.8 Factors for Units Listed Alphabetically and B.9 Factors for units listed by kind of quantity or field of science.

Lide, David R., Daniel (Editor-in-Chief). CRC Handbook of Chemistry and Physics, 89th Edition New York, NY: CRC Press, p. 1-28, 2008.

Wikipedia contributors. "Conversion of units" Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, last visited 26 Jun. 2011.

How Many? A dictionary of units of measurement at http://www.unc.edu/~rowlett/units/