# ETT Size Calculator (Endotracheal Tube Size and Depth)

URL: https://speedycalculator.com/calculators/health/ett-size/
Last updated: 2026-10-30

> The ETT size calculator estimates endotracheal tube internal diameter and insertion depth for children by age (cuffed and uncuffed) and gives typical adult sizes, using the formulas from paediatric life-support courses.

## Inputs

- Patient
- Age (years)

## Results

- Uncuffed tube size (children) or larger adult size
- Cuffed tube size
- Oral insertion depth at the lips
- Nasal insertion depth

## 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)
```

## Explanation

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

FieldWhat to enterPatientChoose one: Child (1–10 years), Adult woman, Adult manAgeIn 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)2434.344.554.86585.5
*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.*

## 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.

## FAQ

**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.


## Sources

- [Resuscitation Council UK – Paediatric advanced life support](https://www.resus.org.uk/library/2021-resuscitation-guidelines/paediatric-advanced-life-support-guidelines)