Catheters come in different shapes and sizes. The size of the catheter will differ depending on your specific needs and requirements.
The diameter of a catheter is measured in “French Units” or “Fr”. A single French Unit (1 FR) is 0.33mm.
1 FR = 0.33mm = .013” (or 1/77”)
Here is a sizing scale measuring the outside diameter for catheters in French Units:
Foley Catheters also have a measurement for their balloon capacity. This measurement is in cubic centimeters and translates directly into milliliters.
1 CC = 1 mL