Answers.Body: <p>The answer depends on preference:</p>
  <ul>
  <li>If you apply a 50-move limit, the longest possible chess game is 5898.5 moves long.</li>
  <li>If you apply a 75-move limit, it is 8848.5 moves long.</li>
  </ul>
  <p>See https://wismuth.com/chess/longest-game.html for a detailed demonstration.</p>
  <p>If you don't apply either of these, the next hurdle is draw by repetition (at 3 or 5 occurrences). I don't know if anyone has explored this systematically: perhaps a project for someone?</p>
  <p>If you reject draw by repetition too, then you can carry on forever. Have a look at https://wismuth.com/chess/statistics-games.html#perft-ratios which argues that the maximum eigenvalue of chess (which will dominate the growth rate in the long run) is about 84.3.</p>
  <p>Which approach is right?</p>
  <ul>
  <li>If you are a player, then I guess you might say that the 50-move rule involves player choice, while the 75-move rule is mandatory, so go for the latter.</li>
  <li>If you are a problemist, you might say that the 50-move rule only applies by default to retro problems. However you would probably be interested to waive that convention for this interesting problem. I don't know any problemists who are adopting the 75-move rule yet, and it's excluded from scope of conventions.</li>
  </ul>
  
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Answers.UserDisplayName: Laska
Answers.Body: <ol>
  <li><p>49 as black and white move knights.</p>
  </li>
  <li><p>32 * 50 = 1600; to lock the pawns up. In this case, White pushes each pawn 1 time until it is stopped by a black pawn.</p>
  </li>
  <li><p>6 * 50 * 8 = 2400; the white pawns are devoured one at a time, and as a black pawn is unblocked, it runs down the board, one square at a time.  They promote to Knights.</p>
  </li>
  <li><p>7 * 50 = 350; each of the new knights are devoured.</p>
  </li>
  <li><p>30 * 50 = 1500; the rest of the pieces are devoured.  Kings have to be left standing, so 30 here, not 31.</p>
  </li>
  </ol>
  <p>The sum of these moves is 5899. Although in order to practically make this happen, both sides will have to lose one tempo capturing the last remaining piece of their opponents, leaving us with 5898 total moves. For an example demonstration of how this works out, <a href="https://www.youtube.com/watch?v=D5DXJxR3Uig" rel="nofollow noreferrer">check out this youtube video</a>.</p>
  
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Answers.Text: You seem to have very many "rest of the pieces". With all the pawns taken (promoted or otherwise), there are 14 capturable pieces left, not 30. Also, capturing a pawn is always a mistake, that pawn still had many game-lengthening moves left in it. It's better to promote every pawn, and sacrifice other pieces to help the pawns pass each other.
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Answers.Text: 6. King vs King is an automatic draw due to lack of materiel to cause a checkmate. Maximum is 5899.
Answers.UserDisplayName: Hans Z
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Answers.Text: Is that in the FIDE rules?
Answers.UserDisplayName: Tony Ennis
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Answers.Text: Article 9.6- The game is drawn when a position is reached from which a checkmate cannot occur by any possible series of legal moves. This immediately ends the game, provided that the move producing this position was legal.
Answers.UserDisplayName: Hans Z
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Answers.UserDisplayName: Tony Ennis
Answers.Body: <p>Ian Stewart discusses in an October 1995 Scientific American <a href="http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&amp;ARTICLEID_CHAR=92BAD476-31C4-43CE-BC0F-57966F4ED67" rel="nofollow noreferrer">column</a> how chess can be played with an infinite number of moves (and thus have a game that never ends).</p>
  <blockquote>
  <p>Anyone who plays chess knows that some games just peter out : neither player seems able to win, nothing constructive can be done and there is no obvious way to end the game. If neither player agrees to a draw, the game might go on indefinitely. Foreseeing such situations, the bodies that frame the laws of chess have proposed many different rules to force games to end. The classic law states that the game shall be drawn if a player proves that 50 moves have been made on each side, checkmate has not been given, no men have been captured and no pawn has been moved.</p>
  <p>But recent computer analyses have shown that the rule is not sufficient. There are some endgames in which one player can force a win after 50 moves, when no pieces have been captured and no pawns moved. So the laws of chess must specify certain exceptional situations. Any law that limits the number of moves permitted under particular conditions runs the same risk as the original, and so it would be nice to come up with a different approach altogether.  One proposal, made some time ago, was that the game should end if the same sequence of moves, in exactly the same positions, is repeated three times in a row. (Do not confuse this with the standard law that if the same position occurs three times, the player facing it can claim a draw. But note that this law does not oblige them to do so.)</p>
  </blockquote>
  <p>Stewart then proceeds to create a sequence of two symbols that never repeats a pattern thrice.  He then shows that this sequence can be used by the two players to play a valid endless game even if the proposal becomes official.  (This sequence is called <a href="http://oeis.org/A116178" rel="nofollow noreferrer">Stewart's choral sequence</a>.)</p>
  
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Answers.UserDisplayName: JRN
Answers.Body: <p>There is a cap on the length of a game of chess in terms of the number of moves. That's because of the <a href="http://en.wikipedia.org/wiki/Fifty-move_rule" rel="nofollow">Fifty-Move Rule</a>. Any attempt to draw out a game indefinitely would trigger the fifty-move rule and result in a draw. The reason for this is simple. To carry on the game indefinitely, you have to:</p>
  
  <ol>
  <li>Move pawns an infinite number of times: impossible. The number of possible pawn moves is obviously finite as pawns cannot move backward.</li>
  <li>At some point, cease capturing your opponent's figures (otherwise you will capture their king, i.e. checkmate them, ending the game): this will trigger the 50-move rule.</li>
  </ol>
  
  <p>Also, I suggest moving this to Chess.SE.</p>
  
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Answers.Text: A non-ending game of chess is NOT possible if it is subject to the rules in the "Competition Rules" section of the FIDE laws. These contain a 75 move rule and a 5-fold repetition rule that are not claimable and automatically terminate the game.
Answers.UserDisplayName: Martin Rattigan
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Answers.Text: If the game is not subject to the rules in the "Competition Rules" section of the FIDE laws there are no longer a 50 move or a 3-fold repetition rule - those were removed in the laws taking effect from 2017. So no limit on game length in that case.
Answers.UserDisplayName: Martin Rattigan
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Answers.Body: <p>The other answers have relied on the 50 move rule, and have pointed out the possibility of the game not ending if neither player invokes it.</p>
  
  <p>As it is highly unlikely somebody would want to play a game of chess for thousands of moves in a regular game, it follows that such a game would be contrived solely for the purpose of playing out the longest chess game possible.  Furthermore, as nobody would want to spend their entire life playing a game of chess just to hold the record for longest game of chess, this all would be a purely mental exercise.</p>
  
  <p>However, given these constraints and the fact that an unending game of chess is possible if neither player claims a draw from the 50 move rule, it is still unsatisfying to say that a game of chess can go on forever.  Since we cannot substitute chess players, eventually one or the other of the players will die of old age or some other cause and will be unable to continue thereby forfeiting the game or at least bringing it to an end.  We can therefore calculate an upper limit on the number of moves that can be played before this occurs.</p>
  
  <p>Assuming both players learn to play chess earlier than any person yet, say at 3 years old, and live to be older than the oldest person alive, say 120 years old, and that they play every waking moment, say 16 hours per day on average, and play speed chess averaging one move per second, and take only leap days off to rest, this yields an upper bound of 1 move/second * 86400 seconds/day * 365 days/year * 117 years or 3,689,712,000 moves as the longest chess game possible between two people when neither invokes the 50 move rule to claim a draw.</p>
  
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Answers.UserDisplayName: Michael
Answers.Body: <p>According to the &quot;new&quot; FIDE rules, game cannot go to infinity, due to 75 moves rule or automatic draw when a position gets repeated 5 times in a row.
  Since the amount of positions is finite, the games need to be finite as well.</p>
  
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Answers.Text: So what would the maximum game length in moves be? Is it the same formula as with the 50-move rule, but with 75 replacing 50? Or is there an issue caused by the fact that 75 is odd whereas 50 is even?
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Answers.Text: @Rosie F 17697 ply. See https://www.wismuth.com/chess/longest-game.html
Answers.UserDisplayName: Martin Rattigan
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Answers.UserDisplayName: Ferazhu
Answers.Body: <p>Some cleaning up is required, I think:</p>
  
  <p>The number on the website you link to differs from the results published in     Bonsdorff et al., <em>Schach und Zahl.</em> Unterhaltsame Schachmathematik. pp. 11–13.
  There they say that if the 50-move-rule is <em>mandatory</em> the longest possible game (i.e. where both players cooperate to achieve the weird goal of a game of maximal duration) lasts 5899 moves.
  Possibly, the web site used a simpler upper estimate for the "gaps" between pawn moves and captures that cannot be achieved in all occasions.</p>
  
  <p>However, the 50-move-rule (and also the position-repeated-three-times-rule) is <em>not</em> mandatory, i.e. whether or not a player demands remis by that rule is up to him! The players may decide to ignore the rule and play on, thus allowing for an eventually periodic sequence of moves, i.e. an infinite game.</p>
  
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Answers.Text: Please note that the FIDE rules in effect since 1 July 2014 do indeed specify *mandatory* limits (namely, the 75-move rule).
Answers.UserDisplayName: chaosflaws
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Answers.Text: @chaosflaws D'oh, this i show accepted answers become invalidateed over time ... :(
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Answers.Text: No. The FIDE rules explicitly state that after 75 moves the game will be called a draw, even if neither player claims the tp-move rule. This is completely wrong. -1.
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Answers.Text: I’m normally one of the first to reach for the FIDE rules, but they are not required here. The question was about chess games generally, not tournament games. Certainly the maximum number of moves in a tournament game is an interesting question, but calling an answer invalid for failing to consider that question is going too far.
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Answers.Text: The FIDE laws since 2017 only include the 50 move and triple repetition rules under competition rules anyway, so unless the game is played under these rules the points about these rules are not relevant. I don't believe either of these rules has ever been mandatory anyway. Under current competitition rules new mandatory 75 move and quintuple repetition rules limit the game length. See https://www.wismuth.com/chess/longest-game.html.
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Answers.Text: Infinite games are not necessarily periodic. I think only ‮‮latot ni ‮₁ב morf cidoirep era ‮₀א‮ ‮‮‮‮‮‮
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Body: <p>What is the longest chess game possible in terms of chess moves? I read somewhere that there is a theoretical maximum of 5949 moves. But I don't see any proof and I don't think it is correct. </p>
  
  <p>Can it be infinite? </p>
  
  <p><a href="http://www.chess-poster.com/english/notes_and_facts/did_you_know.htm" rel="nofollow noreferrer">Source</a></p>
  
Tags: <records><mathematics>
Title: Longest chess game possible (maximum moves)
ThreadText: # Longest chess game possible (maximum moves)
  
  (Asked by: username_0 on 2013-11-21)
  
  What is the longest chess game possible in terms of chess moves? I read somewhere that there is a theoretical maximum of 5949 moves. But I don't see any proof and I don't think it is correct.
  
  Can it be infinite?
  
  [Source](http://www.chess-poster.com/english/notes_and_facts/did_you_know.htm)
  
  **Tags:** records, mathematics
  
  
  ---
  
  ## 7 answers
  
  ### Answer by username_11 on 2013-11-21. Score: 11 | Accepted answer
  
  Some cleaning up is required, I think:
  
  The number on the website you link to differs from the results published in Bonsdorff et al., *Schach und Zahl.* Unterhaltsame Schachmathematik. pp. 11–13.
  There they say that if the 50-move-rule is *mandatory* the longest possible game (i.e. where both players cooperate to achieve the weird goal of a game of maximal duration) lasts 5899 moves.
  Possibly, the web site used a simpler upper estimate for the "gaps" between pawn moves and captures that cannot be achieved in all occasions.
  
  However, the 50-move-rule (and also the position-repeated-three-times-rule) is *not* mandatory, i.e. whether or not a player demands remis by that rule is up to him! The players may decide to ignore the rule and play on, thus allowing for an eventually periodic sequence of moves, i.e. an infinite game.
  
  > **Comments:**
  > **username_12**: Please note that the FIDE rules in effect since 1 July 2014 do indeed specify *mandatory* limits (namely, the 75-move rule).  
  > **username_11**: @username_12 D'oh, this i show accepted answers become invalidateed over time ... :(  
  > **username_13**: No. The FIDE rules explicitly state that after 75 moves the game will be called a draw, even if neither player claims the tp-move rule. This is completely wrong. -1.  
  > **username_14**: I’m normally one of the first to reach for the FIDE rules, but they are not required here. The question was about chess games generally, not tournament games. Certainly the maximum number of moves in a tournament game is an interesting question, but calling an answer invalid for failing to consider that question is going too far.  
  > **username_7**: The FIDE laws since 2017 only include the 50 move and triple repetition rules under competition rules anyway, so unless the game is played under these rules the points about these rules are not relevant. I don't believe either of these rules has ever been mandatory anyway. Under current competitition rules new mandatory 75 move and quintuple repetition rules limit the game length. See https://www.wismuth.com/chess/longest-game.html.  
  > **username_7**: Infinite games are not necessarily periodic. I think only ‮‮latot ni ‮₁ב morf cidoirep era ‮₀א‮ ‮‮‮‮‮‮  
  
  ---
  
  ### Answer by username_2 on 2013-11-21. Score: 7
  
  1. 49 as black and white move knights.
  2. 32 \* 50 = 1600; to lock the pawns up. In this case, White pushes each pawn 1 time until it is stopped by a black pawn.
  3. 6 \* 50 \* 8 = 2400; the white pawns are devoured one at a time, and as a black pawn is unblocked, it runs down the board, one square at a time. They promote to Knights.
  4. 7 \* 50 = 350; each of the new knights are devoured.
  5. 30 \* 50 = 1500; the rest of the pieces are devoured. Kings have to be left standing, so 30 here, not 31.
  
  The sum of these moves is 5899. Although in order to practically make this happen, both sides will have to lose one tempo capturing the last remaining piece of their opponents, leaving us with 5898 total moves. For an example demonstration of how this works out, [check out this youtube video](https://www.youtube.com/watch?v=D5DXJxR3Uig).
  
  > **Comments:**
  > **username_4**: 6. King vs King is an automatic draw due to lack of materiel to cause a checkmate. Maximum is 5899.  
  > **username_2**: Is that in the FIDE rules?  
  > **username_4**: Article 9.6- The game is drawn when a position is reached from which a checkmate cannot occur by any possible series of legal moves. This immediately ends the game, provided that the move producing this position was legal.  
  > **username_3**: You seem to have very many "rest of the pieces". With all the pawns taken (promoted or otherwise), there are 14 capturable pieces left, not 30. Also, capturing a pawn is always a mistake, that pawn still had many game-lengthening moves left in it. It's better to promote every pawn, and sacrifice other pieces to help the pawns pass each other.  
  
  ---
  
  ### Answer by username_1 on 2019-01-22. Score: 6
  
  The answer depends on preference:
  
  * If you apply a 50-move limit, the longest possible chess game is 5898.5 moves long.
  * If you apply a 75-move limit, it is 8848.5 moves long.
  
  See https://wismuth.com/chess/longest-game.html for a detailed demonstration.
  
  If you don't apply either of these, the next hurdle is draw by repetition (at 3 or 5 occurrences). I don't know if anyone has explored this systematically: perhaps a project for someone?
  
  If you reject draw by repetition too, then you can carry on forever. Have a look at https://wismuth.com/chess/statistics-games.html#perft-ratios which argues that the maximum eigenvalue of chess (which will dominate the growth rate in the long run) is about 84.3.
  
  Which approach is right?
  
  * If you are a player, then I guess you might say that the 50-move rule involves player choice, while the 75-move rule is mandatory, so go for the latter.
  * If you are a problemist, you might say that the 50-move rule only applies by default to retro problems. However you would probably be interested to waive that convention for this interesting problem. I don't know any problemists who are adopting the 75-move rule yet, and it's excluded from scope of conventions.
  
  
  ---
  
  ### Answer by username_5 on 2013-11-21. Score: 4
  
  Ian Stewart discusses in an October 1995 Scientific American [column](http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ARTICLEID_CHAR=92BAD476-31C4-43CE-BC0F-57966F4ED67) how chess can be played with an infinite number of moves (and thus have a game that never ends).
  
  > Anyone who plays chess knows that some games just peter out : neither player seems able to win, nothing constructive can be done and there is no obvious way to end the game. If neither player agrees to a draw, the game might go on indefinitely. Foreseeing such situations, the bodies that frame the laws of chess have proposed many different rules to force games to end. The classic law states that the game shall be drawn if a player proves that 50 moves have been made on each side, checkmate has not been given, no men have been captured and no pawn has been moved.
  >
  > But recent computer analyses have shown that the rule is not sufficient. There are some endgames in which one player can force a win after 50 moves, when no pieces have been captured and no pawns moved. So the laws of chess must specify certain exceptional situations. Any law that limits the number of moves permitted under particular conditions runs the same risk as the original, and so it would be nice to come up with a different approach altogether. One proposal, made some time ago, was that the game should end if the same sequence of moves, in exactly the same positions, is repeated three times in a row. (Do not confuse this with the standard law that if the same position occurs three times, the player facing it can claim a draw. But note that this law does not oblige them to do so.)
  
  Stewart then proceeds to create a sequence of two symbols that never repeats a pattern thrice. He then shows that this sequence can be used by the two players to play a valid endless game even if the proposal becomes official. (This sequence is called [Stewart's choral sequence](http://oeis.org/A116178).)
  
  
  ---
  
  ### Answer by username_6 on 2013-11-21. Score: 3
  
  There is a cap on the length of a game of chess in terms of the number of moves. That's because of the [Fifty-Move Rule](http://en.wikipedia.org/wiki/Fifty-move_rule). Any attempt to draw out a game indefinitely would trigger the fifty-move rule and result in a draw. The reason for this is simple. To carry on the game indefinitely, you have to:
  
  1. Move pawns an infinite number of times: impossible. The number of possible pawn moves is obviously finite as pawns cannot move backward.
  2. At some point, cease capturing your opponent's figures (otherwise you will capture their king, i.e. checkmate them, ending the game): this will trigger the 50-move rule.
  
  Also, I suggest moving this to Chess.SE.
  
  > **Comments:**
  > **username_7**: A non-ending game of chess is NOT possible if it is subject to the rules in the "Competition Rules" section of the FIDE laws. These contain a 75 move rule and a 5-fold repetition rule that are not claimable and automatically terminate the game.  
  > **username_7**: If the game is not subject to the rules in the "Competition Rules" section of the FIDE laws there are no longer a 50 move or a 3-fold repetition rule - those were removed in the laws taking effect from 2017. So no limit on game length in that case.  
  
  ---
  
  ### Answer by username_8 on 2013-11-21. Score: 3
  
  The other answers have relied on the 50 move rule, and have pointed out the possibility of the game not ending if neither player invokes it.
  
  As it is highly unlikely somebody would want to play a game of chess for thousands of moves in a regular game, it follows that such a game would be contrived solely for the purpose of playing out the longest chess game possible. Furthermore, as nobody would want to spend their entire life playing a game of chess just to hold the record for longest game of chess, this all would be a purely mental exercise.
  
  However, given these constraints and the fact that an unending game of chess is possible if neither player claims a draw from the 50 move rule, it is still unsatisfying to say that a game of chess can go on forever. Since we cannot substitute chess players, eventually one or the other of the players will die of old age or some other cause and will be unable to continue thereby forfeiting the game or at least bringing it to an end. We can therefore calculate an upper limit on the number of moves that can be played before this occurs.
  
  Assuming both players learn to play chess earlier than any person yet, say at 3 years old, and live to be older than the oldest person alive, say 120 years old, and that they play every waking moment, say 16 hours per day on average, and play speed chess averaging one move per second, and take only leap days off to rest, this yields an upper bound of 1 move/second \* 86400 seconds/day \* 365 days/year \* 117 years or 3,689,712,000 moves as the longest chess game possible between two people when neither invokes the 50 move rule to claim a draw.
  
  
  ---
  
  ### Answer by username_9 on 2021-08-03. Score: 0
  
  According to the "new" FIDE rules, game cannot go to infinity, due to 75 moves rule or automatic draw when a position gets repeated 5 times in a row.
  Since the amount of positions is finite, the games need to be finite as well.
  
  > **Comments:**
  > **username_10**: So what would the maximum game length in moves be? Is it the same formula as with the 50-move rule, but with 75 replacing 50? Or is there an issue caused by the fact that 75 is odd whereas 50 is even?  
  > **username_7**: @username_10 17697 ply. See https://www.wismuth.com/chess/longest-game.html  
  
  ---
  
  