According to the SI unit, kilogram is the base unit of measurement of mass. It is also the unit of metric system. It is defined as the weight of an international prototype kilograms to milligrams. It is equal to the mass of one liter water. It is the only unit in SI system where it is defined according to the artifact. The other units of the measurement system all the units can be reproduced in the laboratory. 1 kilogram is equal to 10,000 milligrams. In our everyday use we referred it as the weight but actually it is not the weight of any matters it express the mass of that matter. In scientific definition weight is define as the active force experienced any matter by the force of gravity. Where are mass express the whole amount of substance present in matter. The mass of anything be one kilogram then the weight of that thing will be 9.81 Newton. But it totally dependents on the local gravity. But the prototype kilogram is varying this mass with the passing of time. For this reason the international weights and measures committee has take a decision to redefine it. The decision will be taken on 2015.

Generally by the term mass we know that how heavy the substance is. Mass is actually the internal property of any matter. For this property the matter wants to remain at its constant velocity if no any out force does not work on this matter. Sir Isaac Newton introduced a law regarding the mass, F=ma. There m denotes the mass, a denotes the acceleration and f denotes the force. If the acceleration is 1meter/second² and the mass of the matter are 1 kilogram then the total force will be 1 Newton. Weights of any thigh depend on the value of gravity. Weight may be zero but mass never can be zero. Where the value of gravity is equal to zero anything will seem to be weightless.

Because the kilogram underpins in much of the SI units the stability of the IPK is crucial. This is happening the current definition and for the structure. Newton defined the mass with the help of acceleration and the force count in Newton. Many other units regarding the measurement unit of kilogram have been established. Now a day this unit becomes a most important unit in the field of measurement. So the change of this unit may have a bad effect on all units. This is the whole discription about the kilograms to milligrams.