The Kilogram is the fundamental unit of mass in the International System of Units. Previously, when it was created, the kilogram was defined as being equivalent to the mass of one liter of demineralized water at a temperature of fifteen degrees Celsius. Later, this equivalence was abandoned, when it was realized, that the mass of the same amount of water varied according to its purity. Since most of the objects used by man in his day-to-day life are relatively larger than the gram, and since water does not have the same density in all his samples, a standard was required at the commercial level that could be reproduced and maintains its stability. Thus, the mass standard was defined as exactly equal to the mass of a small polished cylinder, fused in 1879 of platinum and iridium, maintained in France, a thousand times greater than the gram, the kilogram.
The Pound is a mass measure used in the imperial system, and is accepted on a daily basis as a unit of weight. The name of the pound is an adaptation of the Latin phrase libra pondo, or a pound of weight. The pound has been used historically to measure the weight of bullets or projectiles in armament and many weapons were named from the name of the shot ammunition. The pound is officially set to equal 453.59237 grams. This equivalence has been in force since 1959 through an international agreement drawn up between the English-speaking countries. There are three different weight systems, the avoirdupois, the troy, and the apothecaries . This multitude of systems presents numerous disadvantages because of the different conversions. This is especially evident if we take into account the widespread use of the metric system, which is much simpler to use and to convert to its sub-units.