The SI unit for mass is grams (g). One teaspoon of sugar would weigh approximately one gram. For heavier objects, kilograms (kg), which is equal to 1000 grams, are used. One kilogram is equal to 2.2 United States pounds.

Mass is the force exerted by the body (molecular compose) without the influence of the gravity. The Mass of a body will be constant even if the gravity changes.

For example:

If a mass of a food packet is 1-kg within the atmosphere of earth; and the same mass will be retained in the moon too. But if a weight of food packet is 9.81 Kg-m sq.sec [Mass * gravity] within the atmosphere of earth, whereas it is 1.62 Kg-m sq.sec, in the surface of moon.

Therefore, Mass is a constant and weight is a dynamic variable.