Answers.Body: <blockquote>
  <p>But, for example, can a 9 round Swiss work with 11 players work?</p>
  </blockquote>
  <p>It can, but there is a good chance that it won't. The problem is something called a &quot;pairing jam&quot;. <a href="https://chess.stackexchange.com/questions/29232/swiss-system-pairing-algorithm-stuck">This question</a> asks what can be done about the problem and my answer expands on the problem and how it is solved in practice (try and anticipate the problem and change the computer pairings early enough to avoid the problem). In my answer I also note that:</p>
  <blockquote>
  <p>For a serious tournament you would not use Swiss pairing when (Number of players) &lt;= (number of rounds + 2).</p>
  </blockquote>
  <p>This rule of thumb was given to me by a senior arbiter I asked about this problem. It suggests that for a 9 round Swiss you need at least 12 players.</p>
  <p>I tried asking a more general question about pairing jams <a href="https://chess.stackexchange.com/questions/40730/how-does-the-likelihood-of-a-pairing-jam-change-as-the-number-of-players-increas">here</a>, but haven't had any replies to this thorny problem . The internet is also strangely silent on the subject.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-07-02T15:00:21.313Z
Answers.Text: Does FIDE allow 11 players in a 10 round Round Robin, with the last round not being played?
Answers.UserDisplayName: Ian Ringrose
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-07-02T14:48:57.777Z
Answers.LastActivityDate: 2024-07-02T14:48:57.777Z
Answers.UserDisplayName: Brian Towers
Body: <p>Clearly with 10 players a 9 round tournament would be a Round Robin, with under 9 players it is likely to be a Double Round Robin.  Swiss tournaments are the normal solution when there are too many players for a Round Robin. But, for example, can a 9 round Swiss work with 11 players work?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-07-02T11:23:26.130Z
Comments.Text: @Lucenaposition There is no requirement that each player play the same number of games in a Swiss.
Comments.UserDisplayName: D M
Tags: <fide><tournament><swiss-pairing>
Title: Minimum number of players for 9 round Swiss tournament?
ThreadText: # Minimum number of players for 9 round Swiss tournament?
  
  (Asked by: username_0 on 2024-07-02)
  
  Clearly with 10 players a 9 round tournament would be a Round Robin, with under 9 players it is likely to be a Double Round Robin. Swiss tournaments are the normal solution when there are too many players for a Round Robin. But, for example, can a 9 round Swiss work with 11 players work?
  
  **Tags:** fide, tournament, swiss-pairing
  
  > **Comments:**
  > **username_1**: @Lucenaposition There is no requirement that each player play the same number of games in a Swiss.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_2 on 2024-07-02. Score: 5 | Accepted answer
  
  > But, for example, can a 9 round Swiss work with 11 players work?
  
  It can, but there is a good chance that it won't. The problem is something called a "pairing jam". [This question](https://chess.stackexchange.com/questions/29232/swiss-system-pairing-algorithm-stuck) asks what can be done about the problem and my answer expands on the problem and how it is solved in practice (try and anticipate the problem and change the computer pairings early enough to avoid the problem). In my answer I also note that:
  
  > For a serious tournament you would not use Swiss pairing when (Number of players) <= (number of rounds + 2).
  
  This rule of thumb was given to me by a senior arbiter I asked about this problem. It suggests that for a 9 round Swiss you need at least 12 players.
  
  I tried asking a more general question about pairing jams [here](https://chess.stackexchange.com/questions/40730/how-does-the-likelihood-of-a-pairing-jam-change-as-the-number-of-players-increas), but haven't had any replies to this thorny problem . The internet is also strangely silent on the subject.
  
  > **Comments:**
  > **username_0**: Does FIDE allow 11 players in a 10 round Round Robin, with the last round not being played?  
  
  ---
  
  