How does Supercell calculate stars in the COC War League?

Clans compete to obtain the most stars, as that is the first criteria for rankings in the league. Aside from stars obtained normally, clans will receive a 10-star bonus for winning a war.

During a League, anyone can view the standings of each clan in the League under "Group", and also the scores of each war in "Rounds", including those wars involving other clans.

Under the "Clan" tab, players can view the statistics of how each member in the roster performed so far in the league, breaking down the number of stars collected by each member, the total destruction accrued, and the number of attacks completed.

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When you win a matchup, you get 10 stars in the overall league. So as an example, let's say you are clan A with 100 total stars playing clan B who had 90 total stars. Clan B beats you by 1 star, so they have 91, you have 100. Well because they won their matchup, they get a bonus of 10 stars, giving them 101, while you stay at 100.