A weighing scale is a device for measuring the weight of an object. Most are Spring Scales and others are just balances that are used to calibrate display weight, since an object's weight is directly proportional to its mass. They are often used to measure the weight of a person, and in many industrial and commercial applications, these are used to determine the weight of things ranging from feathers to loaded tractor-trailers.

In a typical Spring Scale, the spring stretches or compresses in proportion to how hard the Earth pulls down on the object. Every spring will have a proportionality constant that relates how hard you pull it to how far it stretches. It measures force, which is measured in units of force such as pounds-force or Newtons. These scales typically cannot be used for commercial applications unless their springs are temperature compensated or used at a fairly constant temperature. Spring scales which are legal for commerce can be calibrated for the accurate measurement of mass in the location in which they are used and they can give an accurate measurement in kilograms or pounds for this purpose.