Scales are instruments used to measure the weight of objects or substances. They work on the principle of balancing the gravitational force with another force, such as the elastic force of a spring or electromagnetic force, and the measurement is expressed in grams, kilograms, pounds or other units of measurement.

Scales consist of a scale for measuring weight and a measuring mechanism that creates a force that is in balance with the weight of the object being measured. The scale can be analog or digital, and the measuring mechanism can be mechanical, electronic or electromechanical.