Clan Score, also called Clan Points, is what determines the rank of your Clan. You can find your score on your Clan's profile, underneath the Clan badge.
Clan Score is not the sum of all members’ trophies, but instead, it is calculated by weight, according to the following rule:
This means that the first 10 members' trophies have the most important impact on the overall Clan Score. A Clan consisting of very strong top players, with weak players in the lower ranks, has still good chances of a strong overall score.