On this page of the Diablo Immortal guide, you can learn more about CR (Combat Rating) and how to check it out.
What is the Battle Factor?
The Combat Factor reflects the player's combat value . The players most of the time shorten it to CR (Combat Rating). Each new level means more attributes, more health points, and even passive bonuses. However, it becomes obsolete as you reach level 60. Only through Combat Rating you can estimate a player's strength in the later phases of the game. It is influenced by equipped items and upgrades added to them, as well as socketed gems.
How to check your current CR?
To check a player's combat factor, open your inventory and select the little human icon above Inventory.
Now select "More Attributes" to view detailed information about your character's attributes and items. The first item on the list is the Combat Factor.
Another, faster option, but you lose some of the data - open Codex and choose Conquest - there you can find the current Combat Rating.