In endodontics, the term "working width" denotes the cross-sectional measurement of a root canal, specifically at its apex. This is a vital component of endodontic treatment that is frequently underestimated. The appropriate working width is established by using an instrument that is marginally larger than the apical root canal's diameter. This larger tool aids in the removal of the most contaminated dentin and residual pulp from the root canal's apical region.Root canals do not always have a round shape, which can lead to misinterpretations when viewed on two-dimensional radiographs. The internal working width of root canals can be categorized as round, oval, elongated oval, flattened, or irregular. The accurate working width can be determined through a combination of understanding the internal anatomy of teeth and practical experience, using the appropriate manual instruments.If the working width is not correctly determined, it can result in either excessive removal of dentin or insufficient cleaning of the apical region. Hence, a thorough understanding of the working width is essential for successful endodontic treatment.