How ETT size is estimated
For children over age 1, this calculator uses Cole’s formula, a widely taught pediatric estimate: Uncuffed Tube Size (mm internal diameter) = (Age in years / 4) + 4, with cuffed tubes typically sized about 0.5 mm smaller. Infants under 1 year commonly use a fixed estimate around 3.0-3.5 mm, and patients 14 and older typically use standard adult sizes (roughly 7.0-7.5 mm for adult females and 7.5-8.0 mm for adult males).
Estimating insertion depth
A commonly used rule of thumb for oral insertion depth at the lips is roughly three times the internal tube diameter in millimeters, expressed in centimeters.
This calculator is a general educational reference only and is not a substitute for clinical judgment, direct patient assessment, or institutional airway management protocols. Actual tube selection should always be confirmed by trained medical personnel and adjusted based on the individual patient.