What chess position has the most number of possible moves?

What doesn't exist?

Kxb1?

218 legal moves

too bad there are promoted pawns

sdo you include the different types of promotions as different moves?

Hi! I stumbled on this (long dormant) thread earlier today when researching material on the total number of chess positions. Must say that I'm amazed that a definitive answer to this query wasn't found long ago. Anyway, the diagram shows my proposed solution.

The King has 8 moves, as do both knights. Each bishop has 9 moves, each rook has 12 moves. The queen has 17 moves. Six of the pawns have eight moves, the other two pawns have just four moves - 56 pawn moves altogether.

This gives a total of 139.

The total would be the same if the b-pawn and/or the black queen were removed, but it's much more elegant with them on the board. This way all 16 of White's pieces are present and Black is just missing the pawns. I also like it because all Black's pieces are en prise (to promoting pawns and nothing else) and White's threatening mate in one. 

@malu I would like to see that diagram but I couldn't seem to find it on that wikipedia article. Could you post it please?

This has been about theoretical maximum numbers. Does anyone have any stats on how the numbers of moves (average or range) vary through the course of normal chess games?

They increase then decrease.

That's kind of what I expected.

Actual record without promotion pieces : 

If anyone can beat this I suggest you contact Tim Krabbe at the link below, he is a very reliable authority for chess records and chess curiosities, and his website (below) is a great place to kill some time in between pushing wood here. Pls note his record is based on an actual game, not on a composition                            http://timkr.home.xs4all.nl/records/records.htm

Most possible moves: 79

Black to play 
Davis - Panchanathan 
Minneapolis 2005

In the diagram, after White's 23th move, Black had a choice of 79 moves. 

This was a real position played by two chess engines.  It has 110 moves for white, and caused an error in the program:

I haven't checked how many moves this has. It's not a real chess position, and haven't proven this to be the largest number on an 8x8 board.

Qa1a2 Qa1b1 Qa1b2 Qa1c3 Qa1d4 Qa1e5 Qa1f6 Qa1g7 Qc1a3 Qc1b1 Qc1b2 Qc1c2 Qc1c3 Qc1c4 Qc1c5 Qc1c6 Qc1c7 Qc1c8 Qc1d2 Qc1e3 Qc1f4 Qc1g5 Qd1a4 Qd1b3 Qd1c2 Qd1d2 Qd1d3 Qd1d4 Qd1d5 Qd1d6 Qd1d7 Qd1d8 Qd1e1 Qd1e2 Qd1f3 Qd1g4 Qd1h5 Qf1a6 Qf1b5 Qf1c4 Qf1d3 Qf1e1 Qf1e2 Qf1f2 Qf1f3 Qf1f4 Qf1f5 Qf1f6 Qf1f7 Qf1f8 Qf1g1 Qf1g2 Qh3a3 Qh3b3 Qh3c3 Qh3c8 Qh3d3 Qh3d7 Qh3e3 Qh3e6 Qh3f3 Qh3f5 Qh3g2 Qh3g3 Qh3g4 Qh3h2 Qh4a4 Qh4b4 Qh4c4 Qh4d4 Qh4d8 Qh4e1 Qh4e4 Qh4e7 Qh4f2 Qh4f4 Qh4f6 Qh4g3 Qh4g4 Qh4g5 Qh4h5 Qa5a4 Qa5a6 Qa5b4 Qa5b5 Qa5b6 Qa5c3 Qa5c5 Qa5c7 Qa5d2 Qa5d5 Qa5d8 Qa5e1 Qa5e5 Qa5f5 Qa5g5 Qa5h5 Qh6a6 Qh6b6 Qh6c6 Qh6d2 Qh6d6 Qh6e3 Qh6e6 Qh6f4 Qh6f6 Qh6f8 Qh6g5 Qh6g6 Qh6g7 Qh6h5 Qh6h7 Qa7a6 Qb7c6 Qb7d5 Qb7e4 Qb7f3 Qb7g2 Qb8c8 Qe8a4 Qe8b5 Qe8c6 Qe8d7 Qe8d8 Qe8e1 Qe8e2 Qe8e3 Qe8e4 Qe8e5 Qe8e6 Qe8e7 Qe8f7 Qe8f8 Qe8g6 Qe8h5 Qg8a2 Qg8b3 Qg8c4 Qg8d5 Qg8e6 Qg8f7 Qg8f8 Qg8g2 Qg8g3 Qg8g4 Qg8g5 Qg8g6 Qg8g7 Qg8h7 Qh8b2 Qh8c3 Qh8d4 Qh8e5 Qh8f6 Qh8g7 Qh8h7 total amount of possible moves is 156

and for the other player 

Qb1a1 Qb1b2 Qb1b3 Qb1b4 Qb1b5 Qb1b6 Qb1b7 Qb1c1 Qb1c2 Qb1d3 Qb1e4 Qb1f5 Qb1g6 Qe1a5 Qe1b4 Qe1c3 Qe1d1 Qe1d2 Qe1e2 Qe1e3 Qe1e4 Qe1e5 Qe1e6 Qe1e7 Qe1e8 Qe1f1 Qe1f2 Qe1g3 Qe1h4 Qg1f1 Qa2a1 Qa2b2 Qa2b3 Qa2c2 Qa2c4 Qa2d2 Qa2d5 Qa2e2 Qa2e6 Qa2f2 Qa2f7 Qa2g8 Qg2b7 Qg2c6 Qg2d5 Qg2e4 Qg2f3 Qh2h3 Qa3b2 Qa3b3 Qa3b4 Qa3c1 Qa3c3 Qa3c5 Qa3d3 Qa3d6 Qa3e3 Qa3e7 Qa3f3 Qa3g3 Qa3h3 Qa4a5 Qa4b3 Qa4b4 Qa4b5 Qa4c2 Qa4c4 Qa4c6 Qa4d1 Qa4d4 Qa4d7 Qa4e4 Qa4e8 Qa4f4 Qa4g4 Qa4h4 Qh5a5 Qh5b5 Qh5c5 Qh5d1 Qh5d5 Qh5e2 Qh5e5 Qh5e8 Qh5f3 Qh5f5 Qh5f7 Qh5g4 Qh5g5 Qh5g6 Qh5h4 Qh5h6 Qa6a5 Qa6a7 Qa6b5 Qa6b6 Qa6b7 Qa6c4 Qa6c6 Qa6d3 Qa6d6 Qa6e2 Qa6e6 Qa6f1 Qa6f6 Qa6g6 Qa6h6 Qh7b7 Qh7c2 Qh7c7 Qh7d3 Qh7d7 Qh7e4 Qh7e7 Qh7f5 Qh7f7 Qh7g6 Qh7g7 Qh7g8 Qh7h6 Qh7h8 Qc8b7 Qc8b8 Qc8c1 Qc8c2 Qc8c3 Qc8c4 Qc8c5 Qc8c6 Qc8c7 Qc8d7 Qc8e6 Qc8f5 Qc8g4 Qc8h3 Qd8a5 Qd8b6 Qd8c7 Qd8d1 Qd8d2 Qd8d3 Qd8d4 Qd8d5 Qd8d6 Qd8d7 Qd8e7 Qd8e8 Qd8f6 Qd8g5 Qd8h4 Qf8b4 Qf8c5 Qf8d6 Qf8e7 Qf8e8 Qf8f1 Qf8f2 Qf8f3 Qf8f4 Qf8f5 Qf8f6 Qf8f7 Qf8g7 Qf8g8 Qf8h6 total amount of possible moves is 165

To answer your board configuration question above 

Here is a legal game sequence I just put together.  Black promotes one queen just for fun, but White does not promote any pawns.  In the final position, White has 141 legal moves.