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ETT size and depth (pediatric)

Age in years (a 6-month-old is 0.5). Also accepts months or days. These formulas apply roughly 1–10 years; below ~1 year use weight/gestational-age neonatal sizing instead, and above ~12 years use adult sizing.

Independent clinical validation: pending

Two independent clinical validators will be named here once review is complete.

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How it is calculated

Uncuffed internal diameter (mm) = age in years ÷ 4 + 4 (Cole). Cuffed internal diameter (mm) = age in years ÷ 4 + 3.5 (APLS/Motoyama/Duracher). Oral insertion depth at the lips (cm) = age in years ÷ 2 + 12. These are estimates: round the tube diameter to the nearest available 0.5 mm size, keep tubes 0.5 mm larger and smaller on hand, and confirm placement by air-leak test, auscultation, capnography, chest rise, and imaging. A depth cross-check is tube ID (mm) × 3, which should agree with age ÷ 2 + 12 within about 1 cm.

Limitations and notes

Estimation formulas, not a severity score — no interpretation bands apply (interpretation is intentionally empty). Cuffed constant is pinned to +3.5 (APLS/Motoyama/Duracher 2008, PMID 18184241); the classic Khine +3.0 (PMID 9066329) yields a tube 0.5 mm smaller and is still widely taught — recorded here per the pin-the-constant requirement. Round each raw internal diameter to the nearest manufactured 0.5 mm step and keep tubes 0.5 mm larger and smaller available; the age formulas mis-size a meaningful minority of children (Cole tends to over-size the youngest in range), so always confirm fit clinically (uncuffed air-leak conventionally audible at ~20–30 cmH₂O). Domain is roughly 1–10 (up to ~12) years: below ~1 year, sizing/depth are weight- and gestational-age-based (Merck/NRP table; Kempley 2008, PMID 18372092) and are NOT computed here; above ~12 years use adult sizing. Only the ORAL depth formula is emitted. NEEDS SOURCE (carried from research): the nasal-route depth offset (~+2–3 cm) is not verified from a primary source, and the fixed infant depth steps (~10/11/12 cm) lack primary APLS pagination — neither is implemented here.

Accepted input ranges

  • Age — 0–12 years

References

  1. Cole F. Pediatric formulas for the anesthesiologist. AMA J Dis Child. 1957;94(6):672–673.PMID 13478300DOI 10.1001/archpedi.1957.04030070084009
  2. Khine HH, et al. Comparison of cuffed and uncuffed endotracheal tubes in young children during general anesthesia. Anesthesiology. 1997;86(3):627–631.PMID 9066329DOI 10.1097/00000542-199703000-00015
  3. Duracher C, et al. Evaluation of cuffed tracheal tube size predicted using the Khine formula in children. Paediatr Anaesth. 2008;18(2):113–118.PMID 18184241DOI 10.1111/j.1460-9592.2007.02382.x
  4. Weber MD, et al. Recommendations for endotracheal tube insertion depths in children. Respir Care. 2023.PMID 37336629
  5. Endotracheal Tube. StatPearls [Internet]. NCBI Bookshelf NBK539747.Source

Version and changelog

v1.0.0 · Airway and equipment

  • 2026-07-25 v1.0.0 — Initial release: pediatric ETT cuffed/uncuffed internal diameter and oral depth from age formulas.

Important

For use by qualified health professionals as an informational and educational aid. It supports clinical judgment and does not replace it. Verify every result independently before making a clinical decision. This is not a medical device.