When working with sheet metal, it is common for the term “gauge” to be used. Someone unfamiliar with the gauge system may not understand what is meant by 18 gauge steel, for example. To help, this blog will explain the gauge system and features a sheet metal gauge chart.

How are sheet metal gauges used?

Gauges are used to specify the thickness of a sheet metal. Gauges are neither standard nor metric and the values are independent of those measurement systems. A gauge conversion chart can be used to determine the actual thickness of sheet metal in inches or millimeters. For example, 18 gauge steel, according to a gauge conversion chart, is 0.0478 inch or 1.214 millimeter. The gauge number “18” holds no relevance to the actual measurements.

There are several different gauge systems used today, with specific gauge designations used for specific metal types. For example, in one gauge system, 18 gauge steel measures 0.0478 inches thick, but 18 gauge aluminium is 0.0403 inches thick. Because of the varying thicknesses, a gauge chart should be used to ensure the metal meets the required dimensions.

History of the gauge system

The gauge system has long history in metal fabrication. It most likely originated from the British wire industry before the standard and metric measurement systems were widely adopted. At that time, gauges were used to describe the diameter of the metal wire being drawn. Since then, it has remained a prevalent method of designating the thickness of both wire and sheet metal.

Sheet Metal Gauge Chart

Gauge Chart
Gauge
Number
Imperial
Equivalent in MM
10 3.25
12 2.64
14 2.03
16 1.63
18 1.22
20 0.91
22 0.71
24 0.56
26 0.46

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