This textbook provides the fundamentals of heat transfer as well as the use of Excel-VBA, from creating macros to custom functions. It establishes a foundation for the rapid and professional execution of calculations and simulations. The guided creation of calculation modules using Excel and VBA from all major areas of heat transfer is the main focus. This includes steady-state heat conduction and steady-state heat transfer, unsteady heat conduction, heat transfer in free and forced convection, as well as radiation and heat transfer during condensation and boiling. Where appropriate and possible, the material property correlations and calculation guidelines from the VDI Heat Atlas are used. For selected applications, more complex designs and simulations of heat transfer processes and heat exchangers are also created. The target audiences are students in bachelor's and master's programs, as well as practitioners in engineering.