The unit used to measure weight in the metric system is the gram. Other metric units for weight include the kilogram, the metric ton and the milligram.
Weight is not equivalent to mass, but in daily usage, weight is a synonym for mass. In the technical and scientific fields, there is a clear differentiation between mass and weight. Weight is the measure of the gravity's force on an object. An object's weight on Earth would differ from that on the Moon because of different gravitational forces.
Scientists define 1 gram as the water mass that fills a 1-centimeter cube. One gram is equivalent to 1,000 milligrams, while 1,000 grams is equivalent to 1 kilogram. One metric ton is equivalent to 1,000 kilograms.