French units (French gauge) is one method for describing the size of catheters. It is the outer circumference of the catheter in millimeters.
Alternative term: Charriere
The French size is about a 3 times the catheter external diameter in mm.
circumference of a circle in mm =
= PI() * (diameter in mm)
French catheter gauge =
= 3 * (external diameter in mm)
1 French is approximately 0.3333 mm.
The luminal diameter of the catheter depends on its wall thickness.
|
French Size |
External Diameter (OD) in mm |
|
3 |
1.0 |
|
4 |
1.35 |
|
5 |
1.67 |
|
6 |
2.0 |
|
7 |
2.3 |
|
8 |
2.7 |
|
9 |
3.0 |
|
10 |
3.3 |
|
11 |
3.7 |
|
12 |
4.0 |
|
13 |
4.3 |
|
14 |
4.7 |
|
15 |
5.0 |
|
16 |
5.3 |
|
17 |
5.7 |
|
18 |
6.0 |
|
19 |
6.3 |
|
20 |
6.7 |
|
22 |
7.3 |
|
24 |
8.0 |
|
26 |
8.7 |
|
28 |
9.3 |
|
30 |
10.0 |
|
32 |
10.7 |
|
34 |
11.3 |
