Here is some very general breakdown of how the peice distribution could be in a chess set...
876 bricks in the set
4 pieces per square : 4 x 64squares = 257
-1? peice used for baseplate
876 - 257 - 1 = 618
618 / 32 chess pieces = 19,3
So each of the chess peiec can use 19,3 bricks.