# Surface/area calculator

 metric GB & USA squared millimeter squared inch squared centimeter squared feet squared meter squared yard are acre hectare squared mile squared kilometer signification: 1 2 3 4 5 6

Use this convertor to convert the units of surface from American/English units to the metrical unit system (SI).

In the calculator mentioned below, you can calculate the area of a circle. You need to fill in the radius. You can also calculate the radius if you fill in the area. It does not matter in what units you fill in. You only have to know that the unit of the surface is derived of the length. If you fill in m, than the surface is m2.

### Definition:

The surface is derived from the length. So The unit of surface (A) is derived from the unit of length. Because the unit of length is the meter (m) and the surface is m · m, the unit of surface is m2.
Source: http://physics.nist.gov/cuu/Units/current.html

### England:

England has had a long time her own metric system. These consist feet, yards, inches, miles etc for length. Just like the SI, the units will be multiplied with each other. For example: yd · yd will be yd2. In 1985 the English went official over to the standard metric systems. You can see this in 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 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 follow conditions:

1. The units in the system should be based on invariable quantities in nature
2. All units, except the basic units, should be derived from the basis units
3. 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).

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