Urinary catheter sizes are usually shown using the Charrière or French scale, written as CH or Fr. The number refers to the catheter's outside diameter rather than its length or balloon size.
This guide explains what CH and Fr mean, how catheter diameter relates to the size number, and how sizes vary across the UNOQUIP urinary catheter range.
Important: This article is intended as a simplified product and terminology guide. Catheter size, length, balloon volume and configuration should be selected according to individual clinical requirements, professional guidance and the manufacturer's instructions for use.
Urinary catheter size chart
As the CH/Fr number increases, the outside diameter of the catheter also increases.
| Catheter size | Approximate outside diameter |
|---|---|
| CH/Fr 6 | 2.0mm |
| CH/Fr 8 | 2.7mm |
| CH/Fr 10 | 3.3mm |
| CH/Fr 12 | 4.0mm |
| CH/Fr 14 | 4.7mm |
| CH/Fr 16 | 5.3mm |
| CH/Fr 18 | 6.0mm |
| CH/Fr 20 | 6.7mm |
| CH/Fr 22 | 7.3mm |
| CH/Fr 24 | 8.0mm |
| CH/Fr 26 | 8.7mm |
The British Association of Urological Surgeons describes urinary catheters as commonly ranging from approximately CH/Fr 6 to CH/Fr 26. The appropriate size depends on the catheter type and clinical requirement.
HOW IS CATHETER SIZE CHOSEN?
Catheter size is selected according to the individual clinical requirement rather than by gender alone. Healthcare professionals generally aim to use the smallest catheter size that still provides adequate drainage.
Typical size ranges can vary depending on whether the catheter is urethral, suprapubic, intermittent, or required for specialist applications such as haematuria or postoperative irrigation.
As a guide, RCN catheter-care guidance lists typical adult urethral sizes of 12–16Ch for men and 12–14Ch for women, with 16–18Ch commonly used for suprapubic catheters. Larger sizes may be required for specialist drainage of blood or clots.
Read the Royal College of Nursing catheter-care guidance
DOES A BIGGER CATHETER NUMBER MEAN A BIGGER CATHETER?
Yes. With the CH/Fr system, a higher number means a larger outside diameter.
This is worth remembering because some other medical sizing systems work in the opposite direction.
RCN catheter-care material advises that catheter size should be based on clinical requirements and that the smallest suitable size should generally be used to provide adequate drainage.
Read the current RCN catheter-care guidance
What catheter sizes are available from UNOQUIP?
The UNOQUIP urinary catheter range covers a broad range of CH/Fr sizes across intermittent, Foley and specialist postoperative catheter configurations.
| UNOQUIP catheter range | Examples of available CH/Fr sizes |
|---|---|
| Intermittent Nelaton Catheters | CH/Fr 6 to 20 |
| Female Nelaton Intermittent Catheters | CH/Fr 6 to 18 |
| Tiemann Intermittent Catheters | CH/Fr 6 to 20 |
| 100% Silicone Foley Catheters – Nelaton, 2-way | CH/Fr 12 to 26 |
| Postoperative Foley Catheters | Available in larger specialist sizes depending on tip and 2-way / 3-way configuration |
These ranges are examples from the current UNOQUIP catalogue. Individual sizes vary by catheter material, length, tip, balloon and configuration, so the relevant product specification should always be checked.
View the UNOQUIP Urinary Catheters catalogue
Explore the UNOQUIP Urological Drainage range
Catheter size is not the same as catheter length
Catheter size is not the same as catheter length
CH or Fr describes the diameter of the catheter. It does not tell you how long the catheter is.
Catheter length is specified separately. For example, the UNOQUIP intermittent range includes standard-length Nelaton catheters with an effective length of 370mm and female-length Nelaton catheters with an effective length of 200mm.
Similarly, selected UNOQUIP silicone Foley catheter ranges are available in different lengths while retaining the same CH/Fr diameter options.
View UNOQUIP catheter sizes and lengths
Catheter size is not the same as balloon size
Catheter size is not the same as balloon size
For Foley catheters, catheter diameter and balloon volume are separate specifications.
For example, the standard UNOQUIP 2-way silicone Foley Nelaton range includes CH/Fr 12 through CH/Fr 26 options with a 10ml balloon. Specialist postoperative catheters may use different balloon capacities depending on the product configuration.
The balloon should only be filled according to the volume specified for the individual catheter by the manufacturer.
Check UNOQUIP catheter and balloon specifications
Urinary catheter size FAQs
Is CH the same as Fr?
Yes. CH, meaning Charrière, and Fr, meaning French, are commonly used for the same catheter diameter scale.
What does a 14CH catheter mean?
A CH/Fr 14 catheter has an approximate outside diameter of 4.7mm. The number describes its diameter, not its length or balloon capacity.
Is a 16CH catheter bigger than a 14CH catheter?
Yes. A CH/Fr 16 catheter has an approximate outside diameter of 5.3mm, compared with approximately 4.7mm for CH/Fr 14.
Are male and female catheter sizes different?
Diameter and length are separate specifications. Male / standard and female catheter variants can share the same CH/Fr diameter while having different catheter lengths.
The appropriate size and length should be selected according to the individual catheter requirement and manufacturer guidance.
Why are some postoperative catheters larger?
Specialist postoperative catheters may be available in larger diameters and with larger drainage lumens for applications involving haematuria, blood clots, postoperative drainage or irrigation.
These are specialist configurations and should be selected according to the intended clinical application and relevant product instructions.
Does catheter size tell me the balloon volume?
No. CH/Fr describes the catheter's outside diameter. Balloon capacity is a separate specification stated in millilitres and should be checked on the individual product packaging or manufacturer documentation.
Understanding UNOQUIP catheter sizes
When comparing UNOQUIP urinary catheters, it helps to treat size, length, balloon capacity, material and tip configuration as separate specifications.
A product described as CH/Fr 14, for example, tells you its outside diameter. It does not by itself identify whether the catheter is male or female length, intermittent or indwelling, 2-way or 3-way, or what balloon capacity it has.
Explore the UNOQUIP urinary catheter range
View the UNOQUIP Urinary Catheters catalogue
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