1 bit for each square represent there is a piece on that pos so 64 bits
then for each side, 4 bits to represent number of pieces and 3 bits for each piece to represent their type
At max 64 + 2x(4 + 3 x 16)=168 bits for 16 pieces each side.
edit: nvm this wouldn't work since you wouldn't know the colors of the pieces on board. You need to store 4 bits for each piece, 1 color + 3 type so it is 64 + 2 * 4 * 16 = 196. I am not sure if this is better anymore
1 bit for each square represent there is a piece on that pos so 64 bits
then for each side, 4 bits to represent number of pieces and 3 bits for each piece to represent their type
At max 64 + 2x(4 + 3 x 16)=168 bits for 16 pieces each side.
edit: nvm this wouldn't work since you wouldn't know the colors of the pieces on board. You need to store 4 bits for each piece, 1 color + 3 type so it is 64 + 2 * 4 * 16 = 196. I am not sure if this is better anymore