Taking the mystery out of surface impedance boundary conditions (SIBCs), this book provides an understanding of SIBCs that helps practitioners to select, use, and develop impedance boundary conditions for their own applications. It presents theoretical arguments and mathematical relationships, but the focus of the text remains practical. The book includes well-known numerical techniques and formulations of SIBCs and demonstrates implementation in new or existing code. Discussing SIBCs using a comprehensive approach, the authors provide simple decision tools that allow readers to decide if and how an SIBC can be used and presents theoretical and experimental validation of the proposed SIBCs.