Understanding Catheter Sizes

One of the things you’ll have to figure out as a catheter user is which size is best for you. Whether you use an intermittent catheter with a coude tip or a foley catheter, there are a few key measurements that you’ll have to look for.

The diameter of the catheter, its length, and the balloon size (if using a foley catheter) are all important to having a safe and easy cath experience. With UTIs being a common side effect of using catheters, being knowledgeable about catheters will help you be proactive about your health.

Understanding the French Catheter Scale

The external diameter of catheters is most commonly measured in “french units,” which are shown as “fr.” Catheters that come with funnel ends are color coded to indicate their size.

Catheter size and color chart

Color French units Millimeters
orange 6 2.0
red 8 2.7
yellow 10 3.3
white 12 4.0
green 14 4.7
orange 16 5.3
red 18 6.0
yellow 20 6.7
purple 22 7.3
blue 24 8.0
black 26 8.7

This system is universal. Straight and coude tip catheters use this sizing system, as well as indwelling catheters.

Foley Catheter Sizes

In addition to external diameter, foley catheters have two other measurements you should be looking for: length and balloon size. Because the male urethra is longer than the female one, catheter length is often described as “male” or “female.”

For foley catheters, the male length is typically between 40-45cm (approximately 15-17in). Female length is 20-25cm (approximately 7-10in) long.

Indwelling catheters have a balloon on the end that holds the catheter in place inside the bladder. The balloon size is measured in cc’s or milliliters.

Why Catheter Size Matters

No matter what kind of catheter you use, sizing is important. Using the wrong sized catheter can cause injury. For instance, if a man uses a female length foley catheter, it could result in damage to his urethra. Also, catheters that are too big can be difficult to insert.

This is why it’s important to be communicative with your doctor about what you’re experiencing so they can recommend the right catheter for you. Knowing how catheters are sized helps you speak the right language to talk about your care.

The recommendations and information in this material are not medical advice. Contact your healthcare professional for personal medical advice or diagnosis.