Editing Weighing scale (section)

{{Short description|Instrument to measure the weight of an object}}
{{Other uses|Scale (disambiguation)}}
[[File:Balance à tabac 1850.JPG|thumb|Balance scale set, with weights]] 
[[File:Fruit scales.jpg|thumb|Scales used to measure the weight of fruit in a supermarket]]
[[File:Weighing_scale-inTokyo-2022Aug18.webm|thumb|Weighing scale in use in [[Tokyo]]]]
[[File:Digi-keukenweegschaal1284.JPG|thumb|right|Digital kitchen scale, a [[strain gauge]] scale]]
[[File:משקל תינוק.jpg|thumb|Weighing scale for a baby includes a ruler for height measurement]]
A '''scale''' or '''balance''' is a device used to measure [[weight]] or [[mass]]. These are also known as '''mass scales''', '''weight scales''', '''mass balances''', '''massometers''', and '''weight balances'''.

The traditional scale consists of two plates or bowls suspended at equal distances from a [[Lever|fulcrum]]. One plate holds an object of unknown [[mass]] (or [[weight]]), while objects of known mass or weight, called ''[[Weight (object)|weights]]'', are added to the other plate until [[mechanical equilibrium]] is achieved and the plates level off, which happens when the masses on the two plates are equal. The perfect scale rests at neutral. A [[spring scale]] will make use of a [[spring (device)|spring]] of known [[stiffness]] to determine mass (or weight). Suspending a certain mass will extend the spring by a certain amount depending on the spring's stiffness (or [[spring constant]]). The heavier the object, the more the spring stretches, as described in [[Hooke's law]]. Other types of scales making use of different physical principles also exist.

Some scales can be [[calibrate]]d to read in units of force (weight) such as [[newton (unit)|newtons]] instead of units of mass such as [[kilogram]]s. Scales and balances are widely used in commerce, as many products are sold and packaged by mass.