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General product information only, not medical advice. Choosing, fitting or changing a tracheostomy tube is a clinical decision for trained personnel. Always check your product’s labelling and instructions for use (IFU).
A tracheostomy tube size is not one universal number. The same size number means different internal diameters, outer diameters and lengths depending on the manufacturer and the product line, so the chart below lists three manufacturer lines side by side. If you first need the basics, start with what a tracheostomy tube is.
Tracheostomy tube size chart (adult tubes, three product lines)
Dimensions are in millimetres. OC ID is the inner diameter of the outer cannula, IC ID the inner diameter of the inner cannula, and OD the outer diameter of the outer cannula.
| Product line | Size | Length | OC ID | IC ID | OD |
|---|---|---|---|---|---|
| Shiley flexible | 4 | 62 | 6.5 | 5.5 | 9.4 |
| Shiley flexible | 5 | 68 | 7.0 | 6.0 | 10.1 |
| Shiley flexible | 6 | 74 | 7.5 | 6.5 | 10.8 |
| Shiley flexible | 7 | 77 | 8.0 | 7.0 | 11.4 |
| Shiley flexible | 8 | 79 | 8.5 | 7.5 | 12.2 |
| Shiley flexible | 9 | 79 | 9.0 | 8.0 | 12.7 |
| Shiley flexible | 10 | 79 | 10.0 | 9.0 | 13.8 |
| Shiley Legacy | 4 | 62 | 6.7 | 5.0 | 9.4 |
| Shiley Legacy | 6 | 74 | 8.1 | 6.4 | 10.8 |
| Shiley Legacy | 8 | 79 | 9.1 | 7.6 | 12.2 |
| Shiley Legacy | 10 | 79 | 10.7 | 8.9 | 13.8 |
| Portex Regular | 6 | 64 | 6 | 5 | 8.5 |
| Portex Regular | 7 | 70 | 7 | 6 | 9.9 |
| Portex Regular | 8 | 73 | 8 | 7 | 11.3 |
| Portex Regular | 9 | 79 | 9 | 8 | 12.6 |
| Portex Regular | 10 | 79 | 10 | 9 | 14 |
Sources: Shiley flexible rows from the Medtronic sizing information sheet (07/2025, US-RE-2500105), which gives the same values for cuffed and cuffless tubes. Shiley Legacy and Portex Regular rows from the UC Davis Health Otolaryngology compilation of manufacturer specifications (last updated 11/30/2021). Both checked 2026-10-30. Product lines and sizes change, so treat the chart as a reference and confirm against the current catalogue.
How to read the chart
Three measurements are easy to confuse. The outer cannula inner diameter (OC ID) is the open channel the airway passes through. The inner cannula is a removable liner that sits inside the outer cannula, so its inner diameter (IC ID) is always smaller than the OC ID. The outer diameter (OD) is the width of the tube itself and is larger than the OC ID because of the tube wall. Length is listed separately and does not decrease as the size number rises in any of the lines charted.
Decoding a Shiley flexible product code
Medtronic explains its flexible tube codes with the example 4 CN 65 A: the first number is the Jackson size; CN means cuffed and UN uncuffed; the second number is the ISO size, which is the inner diameter of the outer cannula (65 means 6.5 mm); and the last letter shows a disposable inner cannula (A) or a reusable one (R). So 4CN65A is Jackson size 4, cuffed, 6.5 mm outer cannula inner diameter, with a disposable inner cannula.
Equivalence notes: size numbers do not transfer between brands
There is no universal conversion between a “size 6” from one line and another. Taken from the chart above:
| Size 6 in | OC ID (mm) | OD (mm) | Length (mm) |
|---|---|---|---|
| Shiley flexible | 7.5 | 10.8 | 74 |
| Shiley Legacy | 8.1 | 10.8 | 74 |
| Portex Regular | 6 | 8.5 | 64 |
The Shiley flexible size follows the Jackson number while its ISO size tracks the OC ID in tenths of a millimetre, whereas the Portex Regular size number equals the OC ID in millimetres. A size written without a brand and a measurement is therefore ambiguous. The manufacturer documents cited here list millimetre dimensions rather than French (Fr) or gauge equivalents, so none are given.
Common mix-ups
- Inner versus outer diameter. Shiley flexible size 6 has a 7.5 mm OC ID but a 10.8 mm OD; quoting one for the other is a large error.
- Tube ID versus inner cannula ID. The inner cannula is smaller (6.5 mm in the Shiley flexible size 6).
- Jackson size versus ISO size. On Shiley flexible codes the two numbers in the code mean different things (4 versus 65 above).
- Same size number, different line. See the size 6 table above.
Related sizing pages: endotracheal tube sizes (a different device with its own chart), tracheostomy collars and the Passy Muir valve. For other tube and catheter product categories, see catheters and urology supplies.
FAQ
What is a tracheostomy tube?
A tracheostomy tube is a curved tube placed through an opening in the front of the neck into the windpipe to keep an airway open. Tubes are described by inner diameter, outer diameter and length, and may be cuffed or uncuffed. The full explanation is in our guide to what a tracheostomy tube is.
Is there a tracheostomy tube size chart that works for every brand?
No. The chart above shows one size number giving different dimensions in different lines. Use the chart for the manufacturer and product line in question.
What does the inner cannula size mean?
It is the inner diameter of the removable liner inside the outer cannula. It is smaller than the outer cannula inner diameter in every line charted here.
What does a code like 4CN65A mean on a Shiley flexible tube?
Per Medtronic, the first number is the Jackson size, CN or UN shows cuffed or uncuffed, the next two digits are the ISO size (the inner diameter of the outer cannula, so 65 is 6.5 mm), and the last letter shows a disposable (A) or reusable (R) inner cannula. For anything about use, refer to the IFU.
Sources
Checked 2026-10-30.
- Medtronic, “Understanding tracheostomy tube sizing for optimal patient fit: Shiley flexible adult tracheostomy tubes”, 07/2025, US-RE-2500105: https://www.medtronic.com/content/dam/medtronic-wide/public/united-states/products/respiratory/shiley-flexible-tracheostomy-a-sku-sizing-information-sheet.pdf
- UC Davis Health Otolaryngology, “Tracheostomy Tubes with Specifications and Catalogue Reference”, last updated 11/30/2021: https://health.ucdavis.edu/otolaryngology/specialty/Tracheostomy_Tube_Specs_and_Reference.pdf
