A balance is used to measure mass. By multiplying mass by the acceleration due to gravity, the resulting product is the weight of an object at a specific position.
Mass is independent of position, while weight is not. A balance counteracts the difference in weight between a reference weight and a measured weight to give mass, regardless of the magnitude of the acceleration due to gravity. The weights of two objects placed on a scale are reduced to one-sixth of their weight on Earth, meaning a scale will tip the same amount regardless of where the measurement is made.
Mass can also be measured by measuring the acceleration of a body due to the application of a known force. Because force is equal to mass times acceleration, according to Newton’s second law, the application of a known force leads to an acceleration that is inversely proportional to the mass. To conduct an accurate measurement, the magnitude of the net force must be perfectly known, meaning that all frictional and gravitational forces must be accounted for.
Mass can also be inferred knowing the acceleration due to gravity at a specific position then measuring the weight. Dividing weight by acceleration due to gravity gives mass.