For an endodontic therapy to be successful a triad of access cavity preparation, cleaning and shaping and establishing a three–dimensional hermetic obturation is mandatory. Canal preparation is the most important part of the triad that can be very challenging due to the complexities present in the root canal system. Extreme canal curvatures of different degrees within the roots can cause problems as they lead to issues such as ledge formation, separation of instruments, canal blockage and tear‑drop transportation at the apex or perforation. Anatomical variations within the complex root canal morphology are the most commonly seen cause of endodontic treatment failure. It is, therefore, essential to have a good knowledge about the internal and external morphologies of all teeth. The aim of the current paper is to review the methods used to determine the root canal curvature