"Only scores where a user has completed at least 1/5 of the anime/manga are calculated.
Example: If you watched a 26 episode series, this means you would had to have watched at least 5 episodes (26/5.2)=5. We're using 5.2 instead of 5 so we get a whole number for "most" series.
Weighted Rank (WR) = (v / (v + m)) * S + (m / (v + m)) * C
S = Average score for the Anime (mean).
v = Number of votes for the Anime = (Number of people scoring the Anime).
m = Minimum votes/scores required to get a calculated score (currently 50 scores required).
C = The mean score across the entire Anime DB."