The ability to identify heat sources and predict their temperatures across a variety of operating conditions is the key in the design of a reliable electronic system such as a computer, a server, or any other system containing a printed circuit board assembly. The goal of this paper is to investigate a heat sink to come up with a framework to correlate hand calculations and numerical simulations with experimentally obtained results. The thermal design methodology is discussed and a natural convection study of a heat sink is used to demonstrate this thermal design process. Multiple fin heights of a heat sink at different ambient temperatures are analyzed by hand calculations, numerical simulations using ANSYS Icepak 14.0, and a mock-up testing using a copper slug with a Minco heater attached to simulate a processor on a printed circuit board assembly. These three methods can help check upon each other’s accuracy and credibility. Results from the experiment demonstrate how one can improve the accuracy of results by using known correlated data to future investigations. This allows for improved optimization studies and helps reduce design cycle time.