A Weighing scale is an instrument to measure weight of an object. The scale is used to measure the weight of a person, used scientifically to measure the mass of an object, and industrially or commercially to weigh a variety of objects. Some scales measure gravitational force as well as mass.

In physical sciences weight is an interaction of matter with gravitational field. It is equal to the mass of the object multiplied by the gravitational force acting on it. The term weight was first used to describe mass measured by a balance and is still synonymous with mass worldwide. This distinction is not much of a problem as gravitational force is constant all over the earth. (Around 9.8m/s2)

Mass is measured using a balance while a spring scale or a hydraulic or pneumatic scale is used to measure force. Most scales measure weight using a spring. In most countries scientists have adopted SI units, which use Kilogram for mass and Newton for force.

Compared to mass, weight is used commonly everywhere from households to biological and medical sciences. Body weight is measured in kilograms around the world. Sometimes Pounds and Stones are also used. Some even use the weight of an elephant as a comparative unit.

A balance is used to measure accurately the mass of an object. This measuring instrument uses a beam from which a weighing pan and scales pan are suspended. To weigh an object it is placed on the weighing pan and weights are placed on the scales pan until the pans are in equilibrium. Very precise measurements are made possible by ensuring that the fulcrum of the beam is friction free, and by attaching a pointer to the beam, which measures any deviation from the equilibrium position.

In order to avoid large reference weights an off-center beam can be added. To remove the need for small graduated reference weights, a sliding weight called poise can be installed so it can be positioned along a calibrated scale. For large loads, a platform can be floated on a cantilever beam system. Some expensive mechanical scales use dials with counterbalancing weights instead of springs.

A spring scale can measure forces transmitted through the scale in all directions. Some scales such as Jolly balance use a spring with a known spring constant and measure the displacement of the spring due to an object hung by a spring .The linear spring movements are converted to dial readings.

Weight Scales have a number of applications in science, medicine, commerce, household use and sports.