gauge - noun

a measuring instrument for measuring and indicating a quantity such as the thickness of wire or the amount of rain etc.

accepted or approved instance or example of a quantity or quality against which others are judged or measured or compared

the distance between the rails of a railway or between the wheels of a train

the thickness of wire

diameter of a tube or gun barrel

gauge - verb

• judge tentatively or form an estimate of (quantities or time)
• rub to a uniform size
• determine the capacity, volume, or contents of by measurement and calculation
• measure precisely and against a standard
• adapt to a specified measurement
• mix in specific proportions

gauge - thesaurus

approximate   bore   caliber   calibre   estimate   gage   guess   judge