The categories are the same as in the Tour De France or other bike race
What we do is take the grade of the climb and the distance and multiply them. So, for example, a 2 kilometer climb at 4% grade = 8000, and 8000 to 16000 is a category 4 climb. 16 to 32 is a category 3 etc.
Our categorization is based on the official UCI but with some modification.