Choosing the right tube size quickly matters in emergencies. Age formulas apply to children over 1 year; length-based tapes such as Broselow are also widely used. Always have a size smaller and larger ready.
How to use the ETT Size Calculator
- Patient
- Age
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the child’s age in years, or choose adult.
Inputs explained
| Field | What to enter |
|---|---|
| Patient | Choose one: Child (1–10 years), Adult woman, Adult man |
| Age | In years |
Example values
How the main result changes when Age changes and everything else stays at the example values above:
| Age (years) | Cuffed tube size (mm ID) |
|---|---|
| 2 | 4 |
| 3 | 4.3 |
| 4 | 4.5 |
| 5 | 4.8 |
| 6 | 5 |
| 8 | 5.5 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Uncuffed tube ID (mm) = age ÷ 4 + 4
Cuffed tube ID (mm) = age ÷ 4 + 3.5
Oral depth at the lips (cm) = age ÷ 2 + 12, or 3 × tube ID
Adults: women 7.0–7.5 mm (≈ 21 cm), men 7.5–8.0 mm (≈ 23 cm)
Worked example
Inputs — Patient: Child (1–10 years); Age: 4 years.
Results — Uncuffed tube size (children) or larger adult size = 5 mm ID; Cuffed tube size = 4.5 mm ID; Oral insertion depth at the lips = 14 cm; Nasal insertion depth = 17 cm.
Key terms
- ID
- Internal diameter.
Frequently asked questions
Are cuffed tubes used in children?
Yes – modern guidelines favour cuffed tubes in most children, one half size smaller.
How is tube position confirmed?
With waveform capnography, chest movement, auscultation and a chest X-ray.
What about newborns?
Neonates use 2.5–3.5 mm tubes based on weight and gestational age.