Written and maintained by CASRAI Editorial Board
Last updated
General product information only, not medical advice. The tube a patient needs is chosen by their care team; always check the product’s own labelling and instructions for use.
Adult nasogastric (NG) tube sizes are given in French (Fr), and published ranges differ by purpose: a manufacturer guide puts adult tubes at up to 14 Fr, with 8–12 Fr generally used for feeding and larger tubes for drainage, while a university clinical skills manual lists 16 Fr or larger for adult gastric aspiration. The chart below keeps each figure next to the document it comes from, so the disagreement is visible rather than hidden. For background on the device itself, see what a nasogastric tube is.
NG tube sizes for adults: the chart
| Size (Fr) | About (mm)* | What the source says | Source |
|---|---|---|---|
| Up to 14 | up to 4.6 | NG tubes range from 3.5 Fr for neonates to 14 Fr for adults | Compat guide |
| Under 12 | under 4.0 | Tubes described as “small-bore” | Compat guide |
| 8 to 12 | 2.6 to 4.0 | Generally used for feeding | Compat guide |
| Over 12 | over 4.0 | Generally used for drainage; the larger lumen is less likely to clog | Compat guide |
| Up to 24 | up to 7.9 | Triple-lumen gastric feeding/drainage tubes | Compat guide |
| 16 or larger | 5.3 or more | Adult size listed for gastric aspiration; the largest tube that suits the nostril is selected | LSUHSC manual |
*Millimetres are worked out from 1 Fr = 0.33 mm (Compat); the LSUHSC manual gives the same relationship as one third of a millimetre. Rounded to one decimal.
| Length | What the source says | Source |
|---|---|---|
| 90 to 165 cm | Available lengths for adult NG tubes | Compat guide |
| 90 to 120 cm | Typical gastric feeding tubes | Compat guide |
| 120 to 165 cm | Typical jejunal (nasojejunal) feeding tubes | Compat guide |
How to read French (Fr) sizes
French gauge, also called the Charrière scale (Ch), is the universal system for tube diameter. It measures the outside of the tube: the larger the Fr number, the wider the tube. Each step of 1 Fr adds 0.33 mm of external diameter. Because the number is an outer diameter, two tubes of the same Fr can have different inner lumens. Polyurethane walls can be thinner than silicone, so a polyurethane tube can have a larger lumen at the same outer size (Compat guide).
Feeding vs drainage tubes: why the size differs
Why do published adult ranges disagree?
They describe different jobs. The manufacturer guide separates feeding tubes (8–12 Fr, with small-bore tubes under 12 Fr) from drainage tubes (over 12 Fr, because a larger lumen clogs less). The clinical skills manual is written for gastric aspiration and so lists 16 Fr or larger. Neither figure is a universal “correct” adult size, which is why the chart lists ranges by purpose. For other enteral devices see what a feeding tube is and G-tube buttons.
French vs millimetres
To convert, multiply the Fr number by 0.33 mm (or divide by 3). For example 12 Fr is about 4.0 mm and 16 Fr is about 5.3 mm of outer diameter. This is the only gauge conversion the sources state for NG tubes; do not apply a needle-gauge chart to a French-sized tube.
Common mix-ups
- Size vs length. Fr is diameter; length is listed separately (90–165 cm for adults), and gastric and jejunal tubes differ.
- Material. PVC, silicone and polyurethane are the most common NG tube materials, and the three differ in stiffness and wall thickness (Compat guide). Material is not a size.
- Connector. ENFit is the global enteral-specific connector and is not compatible with IV systems; drainage tubes commonly use funnel connectors, and the older ENLock design predates ENFit (Compat guide). Connector type is not a size.
- Tube type. An NG tube is not an endotracheal tube, and a nasogastric tube differs from a surgically placed tube; see jejunostomy vs gastrostomy tubes.
Regulatory status: the FDA lists “Tube, Nasogastric” as a class 2 device (product code BSS) under 21 CFR 876.5980, gastrointestinal tube and accessories (openFDA classification database and the Code of Federal Regulations, checked 2026-10-30).
Check your product’s labelling. Sizes, lengths, materials and connectors vary by manufacturer and model; the labelling and instructions for use for the exact product are the reference.
FAQ
When to remove an NG tube?
That is a decision for the patient’s care team, not something a size chart settles. The sources used for this guide give no removal guidance, and this page does not cover clinical procedures. Follow the product’s instructions for use and the clinician’s direction.
Do they sedate you for an NG tube?
Whether any sedation or anaesthetic is used is a clinical decision for the care team, and this page does not cover clinical procedures. Ask the treating team what applies in your case.
Which French size is the adult NG tube?
It depends on purpose: up to 14 Fr per the manufacturer guide (8–12 Fr feeding, over 12 Fr drainage), and 16 Fr or larger in the clinical skills manual for gastric aspiration. See the chart above.
Sources
- Compat, A guide for selecting the appropriate nasogastric tube (manufacturer PDF, 31 January 2022), checked 2026-10-30.
- LSUHSC School of Medicine, Clinical Skills Procedure Manual: nasogastric tube, checked 2026-10-30.
- U.S. FDA, openFDA device classification and 21 CFR 876.5980, checked 2026-10-30.
