The most important thing to know about Tri-Clamp (TC) sizing is that the "Size" refers to the outside diameter of the tubing, not the flat flange face.
The Easy Measurement Rule
A Tri-Clamp flange is designed to be approximately 1/2 inch larger than its official name. This extra space allows the gasket and clamp to create a perfectly sanitary, high-pressure seal.
Sizing Cheat Sheet
Use this table to quickly identify your fitting with a standard ruler or calipers:
| If your Flange measures... | Your TC Size is: | Common Applications |
| 0.98" (25mm) | 1/2" or 3/4" (Mini) | Sample valves and carb stones |
| 1.98" (50mm) | 1.5" | Industry Standard for pumps and kettles |
| 2.51" (64mm) | 2.0" | Sanke keg necks and heating elements |
| 3.58" (91mm) | 3.0" | Large fermenter dry-hop ports |