Standard 11 gauge steel is 0.1196 inches thick, and galvanized 11 gauge steel is 0.1233 inches thick, according to the University of North Carolina at Chapel Hill. A full list of steel gauges and their thicknesses are listed in the "How Many? A Dictionary of Units of Measurement" by Russ Rowlett, which is hosted online by the UNC.
The measurement used to describe the thickness of sheet metal is the "gauge" of the metal. If a metal has a high gauge number, it means that the metal is thinner than those with a lower gauge number. The most common gauges of sheet metal are somewhere between 30 and 7. Galvanized 11 gauge sheet metal is most often described as being roughly 1/8 of an inch thick, as detailed in the United States Code according to Cornell.