longest possible game

If players are forced to claim a draw when they can legally do so (for example after 50 moves without a capture or a pawn move), i've calculated that the longest possible chess game has  5783 moves.

Isn't that nice to know? :)

I guess most scorecards will not have enough room to record such a game.

how did you calculate that?

I think you're about 75 moves or so short -- let me dig up my source.

http://blog.chess.com/kurtgodden/the-longest-possible-chess-game

Yeah, I see that others have obtained slightly different numbers. Maybe I'm wrong, but here's what I've done :

The strategy is to always do 49 moves before advancing a pawn or capturing a piece. So each pawn gives you 7 bunches of 49 moves (it advances 6 times, and then you can capture the promoted piece.  The problem is that black and white pawns will run into each other, so to use all pawn moves we need to obtain the following pawn structure:

We need to capture 8 pieces with pawn to obtain this structure. This gives me the following formula :

(16 pawn * 6 pawn moves + 30 pieces captured - 8 pieces captured)*49 +1

=

(6*16+30 -8)*49+1

= 5783

Whereas if players are not forced to draw, if it can go on and on and on, I calculate that the longest possible game on chess.com is theoretically at least 4294967295 moves, depending on the configuration of the server.

epierard, you can look at it this way:

The first capture is done by black on his move number 50 where he takes a white knight with a pawn. That is 49.5 moves without a capture and 0.5 moves with one capture, total 50 moves so far.

This is repeated 2 times taking the two white knights. Total 100 moves so far.

Do you see the point? You need to muliply with 50, not with 49 and neither with 49.5.

***

If you look at the link that TheGrobe provided you will see that the correct amount of moves is 5898. The calculation is: (6*16+30 -8)*50-2 = 5898. You can read further at the link TheGrobe provided (post #5).

***

A note to adamplenty: If the players are not forced to make a draw after 50 moves without a capture or pawn move (or after a 3 fold repetition) there is no limit to the possible lenght of a game.

No computer can store infinite data or count to infinity. Eventually, an integer overflow will occur. 4294967295 moves is when I think it will occur, assuming the program is using a standard 32-bit unsigned integer (there's no point in using a signed integer in this case) as the move counter, and there are no other mechanisms in place to stop the game from playing more than x number of moves. Even if it doesn't overflow, there's still a limit to the amount of data it can store long term (the PGN file will be pretty big after so many moves). So there is a technical limit when played on a computer. However, you are correct in saying there's no limit when playing on a real chess board face-to-face.

If you are saying a computer cannot store infinite data you should also mention that real people will die of old age at some point. If you are waiting for the .pgn to bust the computer's memory chances are this is actually going to happen first.

Actually they might even die of boredom long before move 4294967295.

The longest possible chess game will seem like a short mental exercise you can do on your coffee break in comparison to the longest possible go game.