# How to Convert Gauge Thickness to Millimeters

Gauge in metallurgy is a scale to assess the thickness of the sheet metal produced as thin and flat pieces. The U.S. standard gauge scale was developed in 1893 as a way to estimate tax costs for sheet steel, and remains dominant in machinery and metallurgy. A higher gauge value represents a thinner metal sheet. The difference in one gauge corresponds to the sheet thickness of 0.0156 inches. Use available metal gauge charts and a calculator to convert gauges to millimeters.

Convert Gauge Thickness to Millimeters
1. Open Internet Explorer, Firefox or any other web browser on your computer to navigate to the Gauge and Weight Chart. The link for this chart is below in the Resource section.

2. Find the thickness in inches in the column "US Standard Gauge" that corresponds to a given gauge value; for example, the gauge 30 corresponds to 0.0125 inches.

3. Multiply the thickness in inches by 25.4 to convert the gauge to millimeters. In our example for the gauge 30 the thickness is 0.0125 x 25.4 = 0.3175 millimeters.