This page is for SwissSys v9 to v9.63. See here for SwissSys tie break systems before SwissSys version 9. See here for SwissSys tie break systems after SwissSys version 9.63.
SwissSys Tiebreak Systems Before Version 9.64:
[M] Modified median
Of the two median tiebreaks, this is the more standard now. It evaluates the strength of a player's opposition by summing the final scores of his or her opponents and then discarding either the highest of these scores, the lowest, or both, depending on the tied player's score.
For players who tie with even scores (that is, their number of wins and losses is the same), both high and low are discarded. For tied players with plus scores, only the lowest is discarded, and for players with minus scores only the highest is discarded.
For tournaments of nine or more rounds, the top two scores are discarded (or the bottom two scores, or all four, as determined by the same even/plus/minus criteria above).
These scores are adjusted for any unplayed games, which count a half point each. If the player involved in the tie has any unplayed games, they count as opponents with adjusted scores of 0. (This means that if a player in the tie did not play in a certain round, that round's score of 0 may turn out to be one of the low scores that gets dropped.)
This is just like the Median except that no opponent scores are discarded. Popular with tournaments of only a few rounds.
The Buchholtz systems are FIDE's versions of the median. As with the median, the basic tie break score is just the sum of the opponents final scores. The differences between Buchholtz and the median and Solkoff have to do with how unplayed games are handled. In the Buchholtz systems, if a player involved in the tie has an unplayed game, the tiebreak contribution for the "imaginary" or "virtual" opponent in that round is calculated as the player's own score after that round plus what he would have if all subsequent games had been draws.
The plain Buchholtz system drops no scores, like Solkoff.
[M] Median Buchholtz 1
Median Buchholtz 1 drops 1 high and 1 low. Called Basic Median (Harkness Median) in earlier SwissSys versions.
[M] Median Buchholtz 2
Median Buchholzt 2 drops 2 high and 2 low.
See the FIDE handbook for details on this and other tie break systems.
[C] Cumulative score
This is easy to calculate by hand, and has been popular for that reason. To get this value just add up the cumulative (running) score for each round. The theory is that players who win their games in the early rounds (and therefore end up with higher cumulative scores than players with the same score who win later rounds) have had to face tougher opposition throughout the tournament.
[O] Cumulative scores of opposition
This uses the cumulative scores calculated as above, but for the tied players' opponents rather than for the tied players themselves.
[F] Fide cumulative
This is just like the cumulative, but discards the first X rounds, where X starts at 1, and rises until the tie is broken. You must set the number of rounds to discard whenever you select this tiebreak. However, unlike the other systems available in SwissSys, you can select this tiebreak more than once, specifying a different number of rounds to discard each time.
This system rewards aggressive play by scoring 4 tiebreak points for a win, 2 for a draw, 1 for a loss, and 0 for an unplayed game. For players with equal scores in a tournament, the one with fewer draws will have the better tiebreak score.
[P] Performance of opposition
This method averages the performance rating of the players' opposition. A player's performance rating is calculated by crediting the player with the opponent's rating plus 400 points for wins, minus 400 points for losses, and the opponent's rating for draws.
[A] Average opposition
This averages the ratings of the player's opponents.
[D] Drop-low average opposition
This is just like the average opposition, but it drops the low value before calculating the average.
Head-to-head can be an undependable tiebreak system, and there are three reasons for this, First, there is no way to determine a clear winner in cases where A beats B, B beats C, and C beats A. Second, in ties involving two players, a draw does nothing to resolve the tie. Third, in ties involving more than two players, it is hard to decide a ranking when some players have lost to players in the same scoregroup, but others have not even played against anyone in the scoregroup.
In spite of this, head-to-head is still a popular tiebreak in some circles. SwissSys uses an arbitrary 100 point basis for players, then decreases that value by a point for every game lost against any one of the other tied players.
[T] Total blacks
This straightforward method gives the edge to players who have had to contend with playing black more.
[E] Extra for black (BAP system)
This awards tie break points according to the following system: Win as black = 3, win as white = 2, draw as black = 1, all other results = 0.
[R] Round robin (Sonneborn-Berger)
This system is most often used for round robin events. For each player in the tie, add the final scores of all the opponents the player defeated and half the final scores of all the opponents with whom the player drew.
This is a popular FIDE tiebreak that sums the results against players who scored 50% or better.
[G] Game points (Fixed-roster)
This adds up the individual games won by a team, as opposed to that team's match points.
[U] U.S. amateur
This is another fixed-roster team tiebreak. For each round, the final score of the opposing team is multiplied by the number of points scored against that team. This is recommended over the game point tiebreak listed above because it compensates for lopsided victories against weak teams.
[W] Win count
Another straightforward method which, like the Kashdan system rewards aggressive play.