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Quick Answer
Feeding tube diameter is commonly measured in French units (Fr). One French unit equals approximately 0.33 mm of outer diameter, so a 6 Fr tube measures about 2.0 mm across, while a 24 Fr tube measures about 8.0 mm. The chart below provides a quick reference for comparing common feeding tube sizes.
French Feeding Tube Size Chart
An accurate French feeding tube size chart provides a practical way to compare tube diameter across nasogastric, nasojejunal, gastrostomy, and jejunostomy devices. The French scale is based on outer diameter, with 1 Fr equal to approximately 0.33 mm.
| French Size (Fr) | Approx. Outer Diameter (mm) | General Application Reference |
|---|---|---|
| 6 Fr | 2.0 mm | Very small-bore feeding applications, including selected neonatal use |
| 8 Fr | 2.7 mm | Small-bore enteral feeding applications |
| 10 Fr | 3.3 mm | Small-bore feeding, including selected post-pyloric applications |
| 12 Fr | 4.0 mm | Enteral feeding applications depending on tube design |
| 14 Fr | 4.7 mm | Larger-bore feeding applications and selected gastric access devices |
| 16 Fr | 5.3 mm | Commonly available in selected PEG and gastrostomy tube designs |
| 18 Fr | 6.0 mm | Larger gastrostomy or enteral access devices depending on design |
| 20 Fr | 6.7 mm | Larger-bore gastric access devices depending on intended use |
| 22 Fr | 7.3 mm | Selected larger-bore enteral or gastric access devices |
| 24 Fr | 8.0 mm | Large-bore gastric access applications depending on device design |
The application column is intended as a general reference rather than a fixed clinical rule. The same French size may be used across different feeding tube designs, and actual selection depends on the device, access route, patient needs, formula characteristics, and product specifications.
Using the Chart in Practice
French size is most useful as a quick diameter reference. Smaller Fr numbers indicate a smaller outer diameter, while larger Fr numbers indicate a larger outer diameter. For example, moving from 8 Fr to 16 Fr approximately doubles the tube's outer diameter from 2.7 mm to 5.3 mm.
A larger French size does not automatically mean a better feeding tube. Smaller-bore tubes may be preferred where flexibility and patient tolerance are important, while larger tubes may provide greater lumen capacity depending on the device and intended feeding route.
French size describes the outer diameter only. Two tubes with the same French size can still differ in internal lumen diameter because wall thickness and material vary between products.
How Tube Type Affects Size Selection
The French gauge system is used across different enteral feeding tube types, but tube size should always be interpreted in the context of the device itself.
Nasogastric feeding tubes: Commonly use smaller-bore configurations when the primary purpose is short-term enteral feeding through the nasal route.
Nasojejunal feeding tubes: Often use small-bore designs for post-pyloric feeding, depending on tube construction and intended use.
PEG and gastrostomy tubes: Are available in a wider range of larger French sizes depending on device design and long-term feeding requirements.
Jejunostomy tubes: Size varies according to the tube design, placement route, and feeding requirements.
This is why an Fr-to-mm chart is useful for comparison, but it should not be treated as a universal tube selection guide.
French Size Is Only One Part of Tube Selection
Material composition and design features can change how two feeding tubes with the same French size perform in practice. Polyurethane tubes may use relatively thin walls while maintaining lumen space, while silicone tubes provide a softer and more flexible option in selected enteral applications.
Formula viscosity, medication delivery, flushing practice, expected duration of feeding, placement route, radiopaque markings, and connector configuration may also affect device selection. Feeding tubes, syringes, extension sets, and feeding systems should also be checked for connector compatibility.
For inventory and purchasing teams, the French size provides a consistent way to compare products, but tube type, material, connector design, and intended application still need to be reviewed alongside the nominal Fr size.
Related Feeding Tube Size Guides
- Feeding Tube Sizes for Adults
