In the sanitary fittings marketplace Tri Clamps are sized by the OD of the tube, rather than the size of the flange ferrule. Generally, but not always, the OD of the flange is 1/2” larger than the Tri Clamp size.
An important exception to that standard are the 1/2” and 3/4” Tri Clamps. Both have a flange OD of approximately 1”. Similarly, the 1” and 1 1/2” Tri Clamps both have a flange OD of approximately 2”.
This can allow for different sizes to be connected successfully. However, connection between different size Tri Clamps should only be done by an experienced specialist with understanding of how to use the gasket size for the larger Tri Clamp, and how the connection will impact media conveyance.