In this work, improved heat generation models are developed for straight and tapered shoulder geometries with different tool pin profiles in friction stir welding. The models are developed considering the welding process as a combination of the pure sliding and the pure sticking conditions. From the results, the amount of heat generation is directly proportional to the number of edges in the pin profiles in such a way that the heat generated in the profiles increases from the triangular pin profile to hexagonal pin profile. Also, increase in the tool rotational speed under constant weld speed increases the heat input while increase in the weld speed under constant tool rotational speed decreases the heat input and the rate of heat generation at the shoulder in a flat shoulder tool is more than that of conical/tapered shoulder tool. The predicted results show good agreements with the experimental results in literature.