# Length conversion

 metric GB & USA ångstrom inch nanometer feet micrometer yard millimeter nautical mile centimeter mile decimeter signification: 3 1 2 3 4 5 6 meter hectometer kilometer

Use this conversion calculator to convert the units of length. For example, fill one meter in and see the value of inch, feet or yard and more.

### Definition:

The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second. (17th CGPM (1983), Rés. 1).
Source: http://physics.nist.gov/cuu/Units/current.html

The meter is defined as the distance that a particle of light in vacuum in 299 792 458 s1 travels. This means that when you measure the distance traveled by light in vacuum for one second this distance is exactly one meter. That is convenient, because the definition of the meter is based on a nature constant, the light constant (speed of light), which is 299 792 458 m/s. The remaining derived units are multiplied by a factor 10. These are called prefixes. A prefix may not be used in combination with another prefix (example: a deci centimeter is not allowed, use millimeter). An ångstrom is not a prefix, but it is a factor 10 smaller than a nanometer. The angstrom is only used in distances. See the prefix table

### Earlier definitions of the meter:

The definition that dates back from 1791 is: ten millionth of the length of the meridian of the earth along a quadrant. A quadrant is a quarter of the surface/length of the earth. This was not precise enough, so they made a new definition.

The definition of the meter that dates back from 1889 is based on an piece of artifact. This is the international prototype platinum-iridium. This has the size of one meter.

The definition that dates back from 1960 is based on the wavelength of krypton-86 beam.

Since 1983 the definition of the meter is as above.

### England:

England for a long time had her own metric system. This consists of feet, yards, inches, miles etc. A mile is three times a league, one inch is 12 line and 0.25 hand, 12 inch = 3 feet = 1 yard. In 1985 the English officially went over to the standard metric system. More information in the The Weights and Measures Act 1985 (Metrication) (Amendment) Order 1994.

### United States:

The United States for a long time had their own metric system. Under pressure of the industry the United States converted to the international standard metric system (1988). This was decided in the Omnibus Trade and Competitiveness Act Of 1988. More information in The United States and The Metric System.

### History of SI:

The SI is the abbreviation for Système International d'Unités. Nowadays it is the standard metric system. The SI originated in France. In 1790 the French Academy of Science got an instruction of the National Assemble to design a new standard of unit for the whole world. They decided that the system should be based on the following conditions:

1. The units in the system should be based on invariable quantities in nature
1. All units, except the basic units, should be derived from the basis units
1. Multiplying of the units should go in factors of then (decimals)

Only in 1875 the world was beginning to show some interest in the French development. Because more and more countries were interested in the French system, the Bureau International des Poids et Mesures (BIPM) was founded, nowadays: Conférence Générale des Poids et Mesures (CGPM). In 1960, on the 11th CGPM, the system was named officially International d'Unité. You can see more on http://physics.nist.gov/cuu/Units/history.html, or on the official site of the BIPM: http://www.bipm.fr/enus/3_SI/si-history.html.

### Official organizations:

The institution in The Netherlands that controls the units is Nederlands Meetinstituut (NMi).
The official institution from the world standard of measurements is Conférence Générale des Poids et Mesures (CGPM).
The official institution in the US is The National Institute of Standards & Technology (NIST).
The English institution for measurement standards is the National Physical laboratory (NPL).

National Weights and Measures Laboratory (NWML).

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