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Mass converter

This metric system conversion calculator for weights and measure can be used for converting:

metric US & GB
milligram grain
carat ounce
gram pound
kilogram stone
ton signification:

Use this conversion program to convert units like kilogram to carat of pound or stone as alternative for a metric conversion table / chart.


The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram. (1e CGPM (1889))
Source: http://www.nmi.nl/english/about_metrology/quantities_and_units/definition_of_the_basic_units.htm
Source: http://physics.nist.gov/cuu/Units/current.html

Early definition:

Early the kilogram was defined as the mass of a cubic decimeter water. Since 1901 is the kilogram a block of platinum-iridium saved in France. One liter water weights according the present norms 0.998 kg.

Often the mass and weights are confused with each other. The weight is proportional with the gravitation. On earth is the gravity is not equal everywhere, so the weight is not equal everywhere, but the mass is. If you weigh a mass on the moon, it will be 6 times lighter than on earth, because there is the gravity six times smaller. You can measure the mass in kilograms with a mass balance and the weight with a weigh-beam in Newton. You can calculate the weight with:

F = m*g


= *


F is the weight in N
m = mass in kilogram
g = gravity in m/s2


The mass has a strange unit, because in the unit is a prefix. This is due to the history of the SI. The unit supposed to be equal to one liter of water. This would be called a grave. The volume unit liter is derived from the unit of length. The French thought that the unit was too big and thought that it could give problems with trading and daily use. That is why they have rejected the grave and introduced a new unit. This unit is equal to one milliliter of water. That is 1/1000 of the liter. This new unit got the name gram. This did not seem to be so practical at all and that is why they wanted go back to the grave, but with a new name. The gram was exactly one thousandth of a grave, so the new unit was kilogram, in other words: 1000 gram. That is why there is a prefix in the SI. Later the definition was rejected, because is was not so exact. Nowadays the kilogram is a block of platinum-iridium that is kept in Sèvres, France. This is not in line with the conditions. It is an instable unit, because is isn't based on a nature constant. There is a risk that the value of the kilogram could change. That is why scientists are holding up with the precise definition, but that is very difficult, because it is too difficult to refer on a nature constant.


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
    1. All units, except the basic units, should be derived from the basis units
    1. Multiplying of the units should go in factors of ten (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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