This book examines the foundational theories of chemical kinetics. The first part covers gas-phase kinetics, while the second focuses on reactions in solution. Expounding on the theory, the book explains calculation procedures in detail using modern computational tools, enabling students to directly apply the theories described. Additional chapters and appendices provide background material necessary to apply these theories. Accompanied by detailed examples using Gaussian (with GaussView) and Matlab, this practical hands-on book provides a first step towards doing more sophisticated calculations as part of a research project. Aimed at senior undergraduate and graduate students, this book focuses on theories that provide insights into basic physical principles that govern the rates of chemical reactions.