ETT Size & Depth Estimator

Select population and enter basic demographics to generate weight- and age-based tube sizing recommendations. Always adjust to clinical context.

Population

Sex

Weight (kg)

Height (cm)

Adult Recommendations

ETT internal diameter

8.0 mm

Typical cuffed tube size.

Acceptable range

7.5 – 8.5 mm

Adjust for habitus, airway anatomy, surgical needs.

Depth at teeth (cm)

21.5

Formula: (height / 10) + 4

Depth at nares (cm)

23.0

Add ~1.5 cm for nasal route.

Clinical pearls:

Confirm placement with waveform capnography and chest X-ray (tip ~3–5 cm above carina).
Consider smaller tubes for airway edema, ENT surgery, or mechanical limitations.

How to Use This Calculator

For pediatrics, age and weight are essential; for adults, use sex, height, and weight to tailor ETT size and depth. Apply age- or height-based formulas to determine internal diameter and insertion depth. Adjust for clinical context (difficult airway, surgery type). Verify placement with auscultation, capnography, and imaging. Adjust tube depth to position tip 3–5 cm above carina.

Formula

Adults: typical ID 7.0–8.5 mm (female 7.0–7.5, male 7.5–8.5). Depth ≈ (Height/10) + 4.

Frequently Asked Questions

Consider slightly larger tubes for ventilation resistance, but prioritize airway anatomy. Depth formula remains height-based. Cuffed tubes are now standard even in infants. Consider uncuffed only when cuff pressure monitoring unavailable or specific surgical needs arise. Withdraw until bilateral breath sounds present. Reconfirm after repositioning, especially if patient moved. Use weight-based charts (e.g., 6 + weight (kg) cm). This calculator is best for infants >3 kg and older children. Use corrected age for preterm infants to avoid oversizing tubes; monitor cuff pressure closely.