OutfitTracker uses a standard ELO ranking for every player. ELO is used in many games from chess to CS GO Face it, LOL ... ELO on Wikipedia
Base ELO score for every player is 1000. Every time you kill a player or get killed, the system update your ELO ranking depending on the probability for you to win the duel.
If you win a duel, a small part of the ELO score of your opponent is transfered to your ELO Score. The lower the probability was for you to win, the highter the amount of ELO score is taken from him.
The system gives you more points for killing a player with a greater ELO score, and a very few for killing someone with a much lower ELO score. Outfit Tracker use a dynamic K Factor between 5 and 10, depending on BR delta. This is basically the maximum amount of ELO that can be transferred.
Kills with any types of vehicles and players bellow battle rank 15 are ignored
Your ELO Score slowly decay over time : 300 points will be substracted if you do not play for a period of 10 days. Decay does not happen if your ELO < 1000
Outfit ranking is build on the median value of its active players (played at least once in the last 30 days)