Foley Catheter Sizes, Tip Types & How to Choose the Right One (French Gauge Chart)
May 31, 2026 · 12 min read · Edaochi Medical
The Foley catheter (indwelling balloon urinary catheter) is one of the most-used supplies in any hospital, clinic and ER: it drains the bladder in urinary retention, surgery, ICU urine-output monitoring and long-term care. But when you order, the question isn't "what is it" — it's "which one do I order": what French size, which tip, how many ways (lumens), what balloon and what material. This is a buying and selection guide — not a generic clinical text: it explains how to read the French gauge with a Fr→mm chart, the difference between a straight (Nelaton) tip and a Coudé/Tiemann tip, when to use 2-way vs 3-way, and what to check before buying wholesale. Written for nursing staff, urology, hospital procurement, pharmacies and medical-supply distributors.
What is a Foley catheter and what are its parts?
A Foley catheter is a flexible urinary catheter passed through the urethra into the bladder and held in place by a balloon inflated with sterile water once inside. Unlike a single-use catheter (a straight Nelaton with no balloon), the Foley is indwelling and allows continuous drainage of urine into a collection bag.
Knowing its parts makes ordering clearer:
- Catheter shaft: the main tube, whose outer diameter is measured in French (Fr) gauge.
- Tip: the end that goes in first; either straight (Nelaton) or curved (Coudé/Tiemann).
- Retention balloon: near the tip; inflated (5, 10 or 30 ml) so the catheter cannot slip out.
- Lumens (ways): one to drain and one to inflate the balloon (2-way), or a third for continuous irrigation (3-way).
- Funnel / colour connector: the external end, colour-coded by size, where the bag connects.
Every purchase comes down to four variables: size (Fr), tip type, number of ways and balloon volume. Let's take them one at a time.
For an overview of all catheter families (urinary, suction, vascular), see our guide to the types of catheters first.
French (Fr) catheter sizes: how to read them + conversion chart
Catheter size is measured on the French scale (Fr or CH, Charrière), which expresses the outer circumference. The rule is simple:
1 French = 1/3 of a millimetre of outer diameter. So an 18 Fr catheter is 6 mm across. The higher the number, the thicker the catheter.
To avoid mix-ups, manufacturers colour-code each size on the funnel (international standard):
| Size (Fr) | Outer diameter | Funnel colour | Typical patient |
|---|---|---|---|
| 6 – 10 Fr | 2.0 – 3.3 mm | Paediatric | Children and infants |
| 12 Fr | 4.0 mm | White | Female, clear urine |
| 14 Fr | 4.7 mm | Green | Standard adult (female) |
| 16 Fr | 5.3 mm | Orange | Standard adult (male/female) |
| 18 Fr | 6.0 mm | Red | Male, urine with sediment |
| 20 – 22 Fr | 6.7 – 7.3 mm | Yellow / Violet | Haematuria, clots, post-surgery |
| 24 Fr | 8.0 mm | Blue | Irrigation, large clots |
Practical sizing rules:
- The smallest size that drains well is the best: an over-sized catheter causes discomfort, urethral trauma and blocks the periurethral glands.
- Standard adult: 14–16 Fr covers most cases.
- Blood or clots in urine (haematuria, post-TURP): step up to 18–24 Fr, usually 3-way for irrigation.
- Paediatric: 6–10 Fr.
That's why a department restocking doesn't order "Foley catheters" — it orders a range of sizes (14, 16 and 18 Fr as the core) and reinforces by specialty.
Tip types: straight (Nelaton) vs Coudé / Tiemann
The tip is the second big decision and the source of the most-searched question: straight tip or Coudé tip? The difference is the shape of the leading end.
| Feature | Straight tip (Nelaton) | Coudé / Tiemann tip |
|---|---|---|
| Shape | Straight, rounded end | Curved, tapered, angled end |
| Indication | Routine catheterisation, most patients | Enlarged prostate (BPH), urethral stricture, false passage |
| Advantage | Easier, lower cost, first choice | Negotiates the prostatic obstacle a straight tip can't pass |
| Who uses it most | Females and males without prostate issues | Older men with prostate enlargement, urology |
Key points about the Coudé/Tiemann tip worth knowing when buying and inserting:
- The curved tip must be inserted pointing up (toward the patient's navel), because it follows the natural curve of the male urethra.
- Many Coudé catheters have a guide stripe or marker lined up with the curve so you can orient it without seeing it.
- It is the catheter of choice when a straight tip "won't pass" in an older man: before forcing, switch to a Coudé.
For a distributor or hospital, the usual mix is mostly straight tip (high turnover) plus a smaller stock of Coudé in 16–18 Fr for urology and geriatrics.
2-way vs 3-way, balloon and material: the other two variables
Number of ways (lumens)
- 2-way: the standard catheter. One lumen drains urine, the other inflates the balloon. Covers ~90% of uses: urinary retention, monitoring, general post-op.
- 3-way: adds a third lumen for continuous bladder irrigation. Essential after prostate surgery (TURP), in haematuria with clots, or when the bladder must be flushed. Always a larger size (18–24 Fr).
Balloon volume
| Balloon | Use |
|---|---|
| 5 ml | Paediatric |
| 10 ml (3–5 ml typical real fill, 10 ml nominal) | Adult, general use |
| 30 ml | Haemostasis / traction after prostate surgery, reinforced fixation |
Safety note: inflate the balloon with sterile water only — never air (it floats and won't anchor) and never saline (salt can crystallise and block deflation). Inflate to the volume printed on the funnel.
Material and dwell time
- PVC / coated latex: economical, indicated for short-term use (7–14 days). The highest-turnover option in wards and the ER.
- 100% silicone: more biocompatible, latex-free, less encrustation; indicated for long-term use (up to ~4 weeks) and latex-allergic patients.
Buying rule: for the bulk of hospital consumption, PVC in 14–18 Fr, 2-way, 10 ml balloon; silicone as a separate line for long-stay catheter carriers and latex-allergic patients.
The full system: bed bag, leg bag and catheter kit
A Foley catheter never works alone: it forms a closed drainage system with the collection bag. When planning a purchase, think about the whole system, not just the catheter:
- Bed bag (2000 ml): for the bed-bound or hospitalised patient. Long tube, anti-reflux valve and bottom drain tap; hung below bladder level. Keeping the system closed reduces the risk of catheter-associated urinary tract infection (CAUTI).
- Leg bag (750 / 1000 ml): for the ambulatory or home-care patient. Strapped to the thigh with elastic bands so the patient can walk discreetly during the day. At night it connects to a larger bed bag.
- Catheterisation kit: some services prefer the all-in-one kit (catheter + sterile gloves + lubricant + drape + pre-filled water syringe) to guarantee asepsis and save nursing time in the ER.
For a buyer, defining the full system avoids the classic mistake of having catheters but running out of the right bag type, or mixing incompatible connectors. The ideal is to standardise catheter + bed bag + leg bag from the same supplier to guarantee connector compatibility. To choose between the bed bag and the leg bag, see our urinary drainage bag guide.
What to check before buying wholesale (procurement & distributors)
For a hospital restocking inventory or a medical-supply distributor, these are the points that separate a reliable product from one that generates complaints and returns:
- Size range and colour coding: the supplier should offer F6 to F24 with a standard colour-coded funnel so nursing can identify the size at a glance.
- Tip types: availability of straight (Nelaton) and Coudé/Tiemann tips in the urology sizes (16–18 Fr).
- 2-way and 3-way: both lines, with 3-way in larger sizes for irrigation.
- Leak-free balloon: the most common failure point. Require the balloon to hold inflation without loss; a self-deflating balloon expels the catheter.
- Material and latex: PVC for short-term and a latex-free silicone line for long-term and allergic patients. Must be clearly declared.
- Sterilisation and packaging: sterile (EO), individual pack with indicator and date; protected tip.
- Centimetre markings and universal connector: printed depth markings and a connector compatible with standard bags.
- MOQ, samples and private label (OEM): accessible minimum order, samples for evaluation, and private-label packaging for distributors.
- Regulatory documentation: a manufacturer with a quality system (ISO 13485) and documentation for medical-device registration in your country.
Edaochi Medical manufactures the PVC Foley urinary catheter in F6 to F24, in 2-way and 3-way versions, with 5, 10 and 30 ml balloons, straight or tapered (Tiemann) tip, colour-coded funnel, centimetre markings and EO sterilisation; latex-free line on request. We supply the full system (catheter + 2000 ml bed bag + leg bag) with a compatible connector, low minimum order, samples for evaluation and private-label (OEM) option. Box price and MOQ quote on WhatsApp in under 24 hours.
Frequently Asked Questions
What size Foley catheter is used for an adult?
For a standard adult, 14–16 Fr covers most cases (14 Fr in females, 16 Fr in males). Step up to 18–24 Fr when there is haematuria, clots or after prostate surgery, usually with a 3-way catheter for irrigation. The general rule is to use the smallest size that drains well, to reduce discomfort and urethral trauma.
How do you read French (Fr) catheter sizes?
The French (Fr or CH) measures the outer circumference: 1 Fr equals 1/3 of a millimetre of diameter. So an 18 Fr catheter is 6 mm in outer diameter. The higher the number, the thicker the catheter. Each size also carries a standard funnel colour (e.g. 14 Fr green, 16 Fr orange, 18 Fr red) for quick identification.
When do you use a Coudé tip instead of a straight catheter?
A Coudé/Tiemann (curved) tip is used when a straight catheter cannot pass, typically in older men with an enlarged prostate (BPH), urethral stricture or false passage. It is inserted with the curve pointing up (toward the navel). For routine catheterisation and in females, the straight (Nelaton) tip is the first choice.
What is the difference between a 2-way and a 3-way Foley catheter?
The 2-way has one lumen to drain urine and one to inflate the balloon; it is the standard for retention and general drainage. The 3-way adds a third lumen for continuous bladder irrigation, indicated after prostate surgery (TURP) or in haematuria with clots, and always in larger sizes (18–24 Fr).
What is used to inflate the Foley catheter balloon?
The balloon is inflated with sterile water only, to the volume marked on the funnel (usually 10 ml in adults). It should never be inflated with air, because it can float and fail to anchor the catheter, nor with saline, because salt can crystallise inside the balloon and block deflation on removal.
PVC or silicone catheter — which should I order?
PVC is economical and indicated for short-term use (7–14 days); it is the highest-turnover option in wards and the ER. 100% silicone is more biocompatible, latex-free and resists encrustation better, indicated for long-term catheterisation (up to ~4 weeks) and latex-allergic patients. Most departments keep both lines.
Do you offer a low minimum order and private label (OEM) for distributors?
Yes. Edaochi Medical works with an accessible minimum order even for small clinics, with samples available for evaluation, and offers private-label (OEM) packaging for distributors. We manufacture F6 to F24 in 2-way and 3-way with quality documentation for medical-device registration. A box-price and MOQ quote is delivered on WhatsApp in under 24 hours.
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