The number of possible chess moves has been estimated to be even more than the number of atoms in the universe. The number of atoms in the universe is thought to be as many as 1081, or 10 multiplied by itself 81 times, while the number of possible moves in chess is estimated to be 10120. This calculation for chess movements is known as the Shannon number. The Shannon number includes illegal chess movements and is named after American mathematician Claude Shannon, who calculated this estimation in 1950.
More about chess:
The first chessboard with alternating light and dark squares is thought to date to 1090 A.D. in Europe.
The smallest possible number of chess moves in a complete game is two for each player. A two-move checkmate is often referred to as a “Fool’s mate” because it typically occurs only against very inexperienced or weak opponents.
Chess games are estimated to consist of 30 moves on average, and any game beyond 60 moves is considered very rare.