50%。 The probability of coin toss is 50% heads and 50% tails, that is, half to half. Mathematically speaking, if you toss a coin without a special way, then you will either face up or land face up. The third case is impossible. Mathematician Jacob Bernoulli put forward the famous "Law of Large Numbers" through experimental verification and statistical analysis. In the repeated occurrence of a large number of random events, it often presents an almost inevitable law, which is the law of large numbers. In layman's terms, this theorem is that when the experiment is repeated many times, the frequency of random events approaches its probability. There is a certain inevitability in accident. The conclusion is that every time a coin thrown upward falls, the probability of heads or tails facing up is equal, which is 50%.