Most Magic tournaments use a modified-Swiss pairing system. This means that players will be paired with others with a similar record for a specific number of rounds. After these Swiss rounds, all but the top players are often eliminated. These remaining players then play single elimination. The set of players that are not cut is determined by the system of tiebreakers that tournament Magic uses. I won’t be going into too much detail in this post, but if you are interested in learning more or seeing more examples, you can read about them in Appendix D of the Magic Tournament Rules.
While it may not seem like it, the first tiebreaker is the number of match points that players have. Players receive three points for each match they win, one point for each match they draw, and zero points for each loss.
In some cases, match points alone are enough to figure out the top 8, 64 or 128. However, when they are not, the other tiebreakers come into play. The first one that is used is one that measures the strength of your opponents. In others words, how well did all your opponents do in the event. This is calculated by taking the match-win percentage of each of your opponents and averaging them. For example, if your round one opponent finished the Swiss rounds with a 4-2 record, then his or her win percentage is 66%. Take the win percentage of each of your opponents, add them together and divide by the number of opponents, and you get your opponent match-win percentage. This is the tiebreaker that really matters most of the time. When you’re tied with someone for match points, this is almost always what will determine your final standing.
If you manage to tie a player in both Match points and Opponent’s match-win percentage, the second tiebreaker is your game-win percentage. In other words, it is better for you if you win each match 2-0 as opposed to 2-1. If you win all matches and each match by winning all games, then this tiebreaker would be 100%. If you win each match by winning two games and losing one, then it would be 66%. Drawn games are also factored into this calculation.
The final tiebreaker is similar to the one above, but it measures the game-win percentage of your opponents. It’s pretty rare for this tiebreaker to be necessary, and then only in an extremely large event. It’s good to have just in case you ever need it, though!
There are two final things to note regarding tiebreakers. When a player received a bye, he is considered to have won that match 2-0. This is the case when calculating the player’s match-win and game-win percentage, but is ignored when calculating opponents’ match-win and game-win percentages. Finally, an opponent’s match-win or game-win percentage can never be lower than 33%. If it would be lower that that, it is simply set to 33% instead. This is so a player cannot have his tiebreakers hurt too much by playing against others with very low match and game wins.