18 GA. (.0478 NOM.)
CARBON COLD ROLLED SHEET COMMERCIAL QUALITY ASTM A1008

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 news 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 aluminum is 0.0403 inches thick. Because of the varying thicknesses, a gauge chart should be used to ensure the metal meets the required dimensions.

Mild Steel Gauge Chart*
Gauge Number	Inches	MM
7	.1793	4.554
8	.1644	4.175
9	.1495	3.797
10	.1345	3.416
11	.1196	3.038
12	.1046	2.656
14	.0747	1.897
16	.0598	1.518
18	.0478	1.214
20	.0359	.911
22	.0299	.759
24	.0239	.607
26	.0179	.454
28	.0149	.378