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Calculator: Endotracheal tube size for children (1 to 8 years)

Calculator: Endotracheal tube size for children (1 to 8 years)


Important: Inputs must be complete to perform calculation.

Cuffed ETT internal diameter   mm
Uncuffed ETT internal diameter   mm


  • For both cuffed and uncuffed ETT, additional tubes one half-size larger and one half-size smaller than the size predicted should also be available during endotracheal intubation.
  • For infants younger than 1 year of age and who weigh more than 3.5 kg, select a 3.0 mm internal diameter cuffed ETT or a 3.5 mm internal diameter uncuffed ETT.
  • For cuffed ETTs, measure cuff pressures and maintain <20 cm H2O after intubation.
  • The calculator is based upon the displayed formulas. When the age is an odd number (eg, 1, 3, 5, or 7 years) or is not a whole number (eg, 2.5 years), the calculator rounds the result down to the nearest ETT size.
  • ETT: endotracheal tube.

Equations used
Cuffed endotracheal tube size = 3.5 + (Age/4)
Uncuffed endotracheal tube size = 4 + (Age/4)


Only digits 0 to 9 and a single decimal point (".") are acceptable as numeric inputs. Attempted input of other characters into a numeric field may lead to an incorrect result.

Information on this page may not appear correctly if printed.

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All information contained in and produced by the EBMcalc system is provided for educational purposes only. This information should not be used for the diagnosis or treatment of any health problem or disease. THIS INFORMATION IS NOT INTENDED TO REPLACE CLINICAL JUDGMENT OR GUIDE INDIVIDUAL PATIENT CARE IN ANY MANNER. Click here for full notice and disclaimer.

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