How many possible moves in total can be played in chess?

From the starting position there are 20 possible moves (2 for each of 8 pawns and 2 for each knight). From there the number of permutations increases dramatically. Information theorist Claude Shannon estimated the total number of positions at 10^43, and with there being an average of 35 moves for each side per position, this makes the game tree in the order of 10^123.

This is only positions, though. Since completely different potential move orders can create the same position, this makes the number of iterations much higher. After 1 (2 ply) move by each side, the number is 400 possible move combinations (20 * 20 400). After just 4 moves(8 ply), the number is over 197,000. At 10 moves (20 ply) it grows to 8.350e+28. The number of distinct games, therefore, is unbounded and grows exponentially assuming no threefold repetition and no 50 move rule. Including these two conditions limits the upper possibility at around 366 ply (or 183 full moves).