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Pediatric Airway & Anesthesia

ET Depth Calculator

Estimate pediatric endotracheal tube insertion depth (cm at the lip) using an age-based formula or the weight-based Rule of Seven.

Age-based calculation

Age > 1 yr: Depth (cm) = 12 + (Age ÷ 2). Infants use fixed anchors — newborn ≈ 9 cm, 6 mo ≈ 11.5 cm, 1 yr ≈ 12 cm. The 12 + Age/2 formula is not valid below 1 year.

Patient age (years)

Recommended ET tube depth

Measured at the lip · add 2–3 cm for nasotracheal intubation

Always confirm placement with auscultation, capnography, and chest X-ray.

Weight-based calculation (Rule of Seven)

For neonates/small infants 0.5–4.5 kg: Depth (cm) = 6 + Weight (kg). 1 kg → 7 cm, 2 kg → 8 cm, 3 kg → 9 cm, 4 kg → 10 cm.

Patient weight (kg)

Recommended ET tube depth

Measured at the lip

Rule of Seven is for neonates/small infants 0.5–4.5 kg only. For larger patients use the age-based formula.

Quick reference

Age-based depths

Newborn	9 cm
6 months	11.5 cm
1 year	12 cm
2 years	13 cm
4 years	14 cm
6 years	15 cm
8 years	16 cm
10 years	17 cm
12 years	18 cm

Weight-based (Rule of Seven)

1 kg	7 cm
2 kg	8 cm
3 kg	9 cm
4 kg	10 cm

Clinical considerations

Verification required. Confirm ET tube placement with auscultation, chest rise, capnography, and chest X-ray.

Tube position. Ideal tip position is 2–3 cm above the carina (T2–T4 vertebral level).

Adjustments. May vary with patient anatomy, neck position, and clinical assessment.

Nasal intubation. Add 2–3 cm to the calculated depth for nasotracheal intubation.

Disclaimer. This calculator is for educational and reference use by qualified clinicians only. Endotracheal tube depth is an estimate — always confirm placement clinically. It does not replace clinical judgment or institutional protocols.