Today, traditional mechanical and electrical systems are replaced with special ICT (Information and communication technology) based solutions and with the invention of new technologies; this trend is increasing further more. This special ICT-based domain is called Real-time systems and today’s driveby-wire,electronic stability programs in car, control software in vehicles are just a few examples of real time systems. The task is a fundamental element of the software in a real-time system, and it is always necessary to know the longest execution time of a task, since missing a task’s deadline is a not allowed in a time critical hard real-time system. The longest execution time of a task or the Worst Case Execution Time (WCET) is estimated by WCET analysis. This estimation should be tight and safe to ensure the proper timing behavior of the real time system.There are several methods and tools for WCET analysis.This book is an introduction to WCET along with WCET tools and benchmarking of tools.SWEET(SWEdish Execution Time tool) is used in this book as a WCET tool.An analysis approach with SWEET has been shown in this book ,so that readers can easily get the whole scenario.