Gauge

A gauge is any instrument or standardised system used to measure, check, or maintain a specific dimension — typically thickness, diameter, or clearance. The term applies across many trades: wire gauge measures electrical wire diameter, sheet metal gauge measures thickness, and feeler gauges measure gaps.

Common types

• Wire gauge: A standardised system for specifying wire diameter. In the US, the American Wire Gauge (AWG) system uses numbered sizes where smaller numbers mean thicker wire — 10 AWG is thicker than 20 AWG. In metric systems, wire is specified by cross-sectional area in square millimetres.
• Sheet metal gauge: Similar to wire gauge — lower gauge numbers mean thicker metal. 18-gauge steel is thicker than 24-gauge. The gauge number corresponds to the number of times the metal has been rolled thinner during manufacturing.
• Feeler gauge: A set of thin metal strips of known thickness, used to measure gaps between mating surfaces — valve clearances in engines, spark plug gaps, and bearing clearances.
• Thread gauge: A tool for checking the pitch and diameter of screw threads, ensuring a bolt and nut are compatible.
• Tire pressure gauge: Measures air pressure in tyres, typically in PSI (pounds per square inch) or bar.
• Drill gauge: A plate with numbered holes used to identify the diameter of drill bits.

Why gauges exist

Standardised gauges solve a universal problem: how to specify a dimension precisely and consistently across manufacturers, suppliers, and trades. When an electrician orders 14 AWG wire, every manufacturer in the world knows exactly what diameter that means.