Objectives <p>Optimal placement of an endotracheal tube (ETT) tip is necessary for safe and effective ventilation of the lungs. However, there is no consensus on the most accurate method for calculating the depth of ET insertion. To compare the accuracy (proportion of optimally placed ETT) of nasal–tragus length (NTL)-based formula, body weight-based formula, and gestational age (GA)-based method in estimating the depth of oral ETT insertion in neonates.</p> Methods <p>Neonates of gestational age 25^0/7–41⁺⁶&#xa0;weeks undergoing oral endotracheal intubation during the first 28&#xa0;days of life were randomized into one of three study groups. The depth of ETT insertion was determined using gestational age-based (Kempley), weight-based (Tochen), or NTL-based methods. The optimal position of the ETT tip, assessed by a blinded radiologist on an anteroposterior chest radiograph, was considered to be between the upper border of T1 and the lower border of T2.</p> Results <p>In this study, 165 neonates (55 per group) were included. Birth weight, gestational age, proportion of small-for-gestational age neonates, and other baseline characteristics were similar among neonates in the three groups. The rates of optimal ETT placement were not significantly different between the NTL- (47.2%), GA- (45.4%) and weight-based (43.6%) methods (<i>P</i> = 0.911). The corresponding rates of ETT repositioning in the NTL-, GA- and weight-based method groups based on auscultation of chest was 58%, 49% and 29%, respectively (<i>P</i> &lt; 0.001).</p> Conclusion <p>No significant difference was observed in the accuracy of the three methods studied. Better methods are needed to calculate the depth of ETT insertion.</p> Trial Registration <p>Prospectively registered with the Clinical Trial Registry of India (CTRI/2022/12/048221).</p>