Sheet metal is under ¼ (0. In North America, we measure it in two ways: While Europe and Asia primarily use the metric system, thus millimeters (mm). The gauge system works in reverse. Anything thicker is called a plate. For example. When you need to know the thickness of your metal, a steel gauge chart is your guide. Standard gauge sizes were developed based on the weight of the sheet for a given. Sheet metal is classified based on its thickness, which directly influences its strength, flexibility, and cost. Materials are typically grouped into three categories: Foil or shim: less than 0. Understanding sheet metal gauge charts, thickness measurements in inches and millimeters, and the relationship between gauge. The first step in designing a custom sheet metal cabinet or enclosure is choosing the type and thickness of sheet metal that will be used for its construction.