Endotracheal Tube (ETT) Size Calculator

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Choose pediatric for children aged 1-12 (uses Cole's formula), neonatal for newborns and infants (uses weight-based sizing), or adult for patients 13 years and older.
Patient age in whole years. Cole's formula applies from 1 to 12 years.
years
Cuffed tubes are now preferred even in children when properly sized. Uncuffed tubes remain common under 2 years. Neonatal tubes are always uncuffed.
Recommended ETT sizePediatric - small
4.5mm ID

Inner diameter of the recommended endotracheal tube

Alternative size4mm ID
Oral insertion depth13.5cm
Nasal insertion depth15.5cm
Cuffed size4.5mm ID
Uncuffed size5mm ID
4.5 mm ID
Neonatal<3.5Small pediatric3.5-5Older pediatric5-6.5Adult female6.5-7.5Adult male7.5+

Recommended ETT: 4.5 mm ID

  • Cole's formula for a 4-year-old gives a cuffed ETT size of 4.5 mm ID.
  • Always prepare one tube of the next size down. If the recommended tube passes with a significant air leak, move up 0.5 mm.
  • Target oral insertion depth is approximately 13.5 cm at the lips; nasal route is approximately 15.5 cm at the nare.
  • Confirm tube position with end-tidal CO2 capnography and bilateral auscultation immediately after placement. Obtain a chest X-ray to verify tip position 2-3 cm above the carina.

Next stepThese are estimates only. Clinical factors including anatomical variation, subglottic stenosis, obesity, and emergency conditions may require adjustment. Use clinical judgment and a direct laryngoscopy assessment.

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