What's the age-based ETT size formula?

Uncuffed: (age/4) + 4. Cuffed: (age/4) + 3.5. Use for children older than 1 year; neonates and infants have separate size tables.

What's the depth-at-lip formula?

For children ≥ 2 years: (age/2) + 12 cm. A quick check: tube size × 3 also approximates depth. Adults: 21 cm at lip (women), 23 cm (men).

How do I confirm tube placement?

Waveform capnography with a sustained square-wave pattern is gold standard. Plus bilateral breath sounds, chest rise, no epigastric sounds, and SpO₂ trend.

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ETT size & depth.

Age-based pediatric tube size and depth at lip. Confirm with capnography.

Patient age (years)

Uncuffed size

5.5 mm

Cuffed size

5.0 mm

Depth at lip

15.0 cm

Adult depth rules

Women: 21 cm at the lip (typical range 20–22)
Men: 23 cm at the lip (typical range 22–24)
Confirm with chest rise, breath sounds, and waveform capnography

Neonate / infant sizes

Premature: 2.5 uncuffed, depth 6–8 cm
Term newborn: 3.0–3.5, depth 9–10 cm
6 months: 3.5, depth 10 cm
1 year: 4.0, depth 11 cm

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Frequently asked

What's the age-based ETT size formula?: Uncuffed: (age/4) + 4. Cuffed: (age/4) + 3.5. Use for children older than 1 year; neonates and infants have separate size tables.
What's the depth-at-lip formula?: For children ≥ 2 years: (age/2) + 12 cm. A quick check: tube size × 3 also approximates depth. Adults: 21 cm at lip (women), 23 cm (men).
How do I confirm tube placement?: Waveform capnography with a sustained square-wave pattern is gold standard. Plus bilateral breath sounds, chest rise, no epigastric sounds, and SpO₂ trend.

For educational and exam-preparation use only. Not medical advice. Follow local protocol.