Miles per hour is a unit of speed, expressing the number of international miles covered per hour. The common abbreviation in everyday use is mph, although mi/h, using the SI method of expressing derived units, is sometimes used, especially in the United States. The preferred SI unit for velocity is m/s, although km/h is often used as a replacement for mph.




1 mph is equal to:

  • 0.44704 m/s, the SI derived unit

  • 1.609344 km/h

  • 22/15 =1.4667 feet per second

  • approx. 0.868976 knots

Miles per hour is the unit used for speed limits on roads in the U.S., Britain and various other nations including overseas territories.




                               0.44704 meter
miles per hour = ---------------







                                 0.3048 meter
feet per second = --------------






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Kilometre per hour (American spelling: kilometer per hour) is a unit of both speed (scalar) and velocity (vector). The symbol is km/h or km·h−1. It is often spoken and sometimes written as klicks or kays in slang usage.  By definition, an object travelling at a speed of 1 km/h for an hour would move 1 kilometre.



  • 3.6 km/h ≡ 1 m·s−1, the SI derived unit of speed, metre per second

  • 1 km/h ≈ 0.27778 m/s

  • 1 km/h ≈ 0.62137 mph ≈ 0.91134 feet per second







Blueplanet Ecostar electric racing car with cartridge exchange refueling


The Blueplanet Ecostar in the only land speed record streamliner to be solar powered. It uses DC pancake motors driving all four wheels to produce 400Kw and an expected speed of around 350+ mph. Click on the car to read more.





Knots is how the speed of aircraft and boats is measured. Both miles per hour and knots is a speed which is the number of units of distance that is covered for a certain amount of time.


1 knot = 1 nautical mile per hour = 6076 feet per hour
1 mph =1 mile per hour = 5280 feet per hour


For example, if a train is moving at 50 mph on a track, how would you represent this speed in knots (even though trains are not usually represented in knots)?


To do this problem easily, one can multiply the number of miles per hour that the train is moving by the number of feet per hour that = 1 mph. this converts the speed to a distance traveled in one hour.

That is:-

(50 mph)(5280 feet/ mph)=264,000 feet


Now, divide that distance by the number of feet in a nautical mile (6076).


(264,000 feet)/(6076 feet/ knot) = 43.4 knots



In aerodynamics, speed is also measured by the Mach number, which is the ratio of the speed of the object to the speed of sound. Mach 1 means that you are traveling at the speed of sound or 661.7 knots, or

Mach 1 = 661.7 knots


How would you determine the speed of sound in mph?


661.7 knots = (661.7 nautical miles/hr) (6076 feet/nautical miles)

= 4,020,489.2 feet/hr



(4020489.2 ft/hr)/(5280 ft/mile)=761.5 mph


We can say that Mach 1 = 761.5 mph at sea level.


Since the speed of sound varies with the density of air ( or whatever material it is transmitted through), one needs to determine the density of the air the aircraft is flying through. To compute this, we will use the chart shown below, called the International Civil Aviation Organization Table, or I.C.A.O.

Notice as the altitude increased, the density of air decreases as does the speed of sound in knots.










5 Knots = 5.8 MPH
10 Knots = 11.5 MPH
15 Knots = 17.3 MPH
20 Knots = 23.0 MPH
25 Knots = 28.8 MPH
30 Knots = 34.6 MPH
35 Knots = 40.3 MPH
40 Knots = 46.1 MPH
45 Knots = 51.8 MPH
50 Knots = 57.6 MPH
55 Knots = 63.4 MPH
60 Knots = 69.1 MPH
65 Knots = 74.9 MPH
70 Knots = 80.6 MPH
75 Knots = 86.4 MPH
80 Knots = 92.2 MPH
85 Knots = 97.9 MPH
90 Knots = 103.7 MPH
95 Knots = 109.4 MPH
100 Knots = 115.2 MPH
105 Knots = 121.0 MPH
110 Knots = 126.7 MPH
115 Knots = 132.5 MPH
120 Knots = 138.2 MPH
125 Knots = 144.0 MPH
130 Knots = 149.8 MPH
135 Knots = 155.5 MPH
140 Knots = 161.3 MPH
145 Knots = 167.0 MPH
150 Knots = 172.8 MPH







Windspeed in MPH

 Description - Visible Condition 

Calm smoke rises vertically 
1 - 4  Light air direction of wind shown by smoke but not by wind vanes 
4 - 7  Light breeze wind felt on face; leaves rustle; ordinary wind vane moved by wind 
8 - 12  Gentle breeze leaves and small twigs in constant motion; wind extends light flag 
13 - 18  Moderate breeze raises dust and loose paper; small branches are moved 
19 - 24  Fresh breeze small trees in leaf begin to sway; crested wavelets form on inland water 
25 - 31  Strong breeze large branches in motion; telephone wires whistle; umbrellas used with difficulty 
32 - 38  Moderate gale whole trees in motion; inconvenience in walking against wind 
39 - 46  Fresh gale breaks twigs off trees; generally impedes progress 
47 - 54  Strong gale slight structural damage occurs; chimney pots and slates removed 
55 - 63  Whole gale trees uprooted; considerable structural damage occurs 
64 - 72  Storm very rarely experienced; accompanied by widespread damage 
73+  Hurricane devastation occurs 









  1. Physics. The rate or a measure of the rate of motion, especially:

    1. Distance traveled divided by the time of travel.

    2. The limit of this quotient as the time of travel becomes vanishingly small; the first derivative of distance with respect to time.

    3. The magnitude of a velocity.

  2. Swiftness of action.


    1. The act of moving rapidly.

    2. The state of being in rapid motion; rapidity.

  4. A transmission gear or set of gears in a motor vehicle.


    1. A numerical expression of the sensitivity of a photographic film, plate, or paper to light.

    2. The capacity of a lens to accumulate light at an appropriate aperture.

    3. The length of time required or permitted for a camera shutter to open and admit light.

  6. Slang. A stimulant drug, especially amphetamine or methamphetamine.

  7. Slang. One that suits or appeals to a person's inclinations, skills, or character: Living in a large city is not my speed.

  8. Archaic. Prosperity; luck.

v., sped (spĕd) or speed·ed, speed·ing, speeds.



  1. To cause to go, move, or proceed quickly; hasten.

  2. To increase the speed or rate of; accelerate: speed up a car; sped production.

  3. To wish Godspeed to.

  4. To further, promote, or expedite (a legal action, for example).

  5. Archaic. To help to succeed or prosper; aid.



    1. To go, move, or proceed quickly: sped to the rescue.

    2. To drive at a speed exceeding a legal limit: was speeding on the freeway.

  2. To pass quickly: The days sped by. The months have sped along.

  3. To move, work, or happen at a faster rate; accelerate: His pulse speeded up.

  4. Archaic.

    1. To prove successful; prosper.

    2. To get along in a specified manner; fare.

idiom: up to speed


    1. Operating at maximum speed.

    2. Producing something or performing at an acceptable rate or level.

  2. Informal. Fully informed of or conversant with: I'm not up to speed on these issues yet.


Middle English spede, from Old English spēd, success, swiftness.


SYNONYMS  speed, hurry, hasten, quicken, accelerate, precipitate. These verbs mean to proceed or cause to proceed rapidly or more rapidly. Speed refers to swift motion or action: The train sped through the countryside. Postal workers labored overtime to speed delivery of the holiday mail. Hurry implies a markedly faster rate than usual, often with concomitant confusion or commotion: Hurry, or you'll miss the plane! Don't let anyone hurry you into making a decision. Hasten suggests urgency and often eager or rash swiftness: My doctor hastened to reassure me that the tests were negative. His off-color jokes only hastened his dismissal. Quicken and especially accelerate refer to increase in rate of activity, growth, or progress: The skater's breathing quickened as he neared the end of his routine. The runner quickened her pace as she drew near the finish line. The economic expansion has continued but is no longer accelerating. Heat greatly accelerates the deterioration of perishable foods. Precipitate implies causing something to happen abruptly or prematurely: Mention of the issue precipitated an angry outburst during the meeting. See also synonyms at haste.


WORD HISTORY   We learn from the fable of the tortoise and the hare that the race is not always to the swift, but etymology teaches us that speed and success are closely related. The Old English word spēd, from which our word speed is descended, originally meant “prosperity, successful outcome, ability, or quickness.” A corresponding verb, spēdan, in Modern English the verb speed, meant “to succeed, prosper, or achieve a goal”; and an adjective, spēdig, the ancestor of our word speedy, meant “wealthy, powerful.” Except for archaic uses the words today relate only to the general sense of “velocity.” The meaning “success” is retained chiefly in the compound Godspeed, a noun formed from the phrase meaning “May God cause you to prosper.”




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