Endotracheal Tube Size Calculator

Endotracheal tube selection is a critical part of pediatric airway management. This calculator applies commonly taught age-based formulas to provide a starting internal diameter for cuffed and uncuffed tubes and an initial oral insertion depth. For children from one through sixteen years, the uncuffed estimate is age divided by four plus four millimeters. The cuffed estimate is age divided by four plus three and one-half millimeters. Results are rounded to the nearest half millimeter because tubes are commonly stocked in half-size increments. The oral depth estimate uses age divided by two plus twelve centimeters. It is only an initial guide. Tube depth must be assessed after placement with direct visualization through the vocal cords, continuous waveform capnography, symmetric chest movement and breath sounds, oxygenation, and the confirmation method required by the clinical setting. Head and neck movement can shift a pediatric tube substantially, so position needs reassessment after movement, transport, or a change in ventilation. Age formulas do not capture every airway. A child's anatomy, height, weight, airway swelling, congenital conditions, trauma, prior surgery, and the specific tube design may change the best choice. Neonates and infants younger than one year require weight- or gestational-age-based guidance and are deliberately outside this calculator. Adolescents with adult body size may be better served by adult selection practices. Clinicians should prepare the calculated size plus at least one size smaller and one size larger before attempting intubation. A cuffed tube should permit ventilation without excessive cuff pressure. Use a cuff-pressure manometer and follow device and institutional guidance. An uncuffed tube should provide an appropriate leak at the pressure used in local practice. Resistance during passage is a warning to stop rather than force the tube. Emergency airway management requires training, appropriate monitoring, rescue equipment, and a backup plan. This result is an educational cross-check for qualified professionals, not instructions for untrained intubation or a substitute for clinical judgment.