43 Heads in a Row on a Fair Coin
The chance of 43 heads in a row on a fair coin is 1.14 × 10-11%, or 1 in 8.8 trillion. Tails is exactly the same, and so is a run of any one side you pick in advance: each flip is a 50% chance, so 43 in a row is 0.5 multiplied by itself 43 times.
The odds of 43 in a row
| Measure | Value |
|---|---|
| Chance of 43 heads from a given flip | 1.14 × 10-11% |
| Odds | 1 in 8.8 trillion |
| Flips to wait for it, on average | 17.59 trillion |
| Chance of 43 heads OR 43 tails starting on a given flip | 2.27 × 10-11% |
| Chance a run of 43 appears at least once in 100 flips | 3.35 × 10-10% |
| Chance a run of 43 appears at least once in 1,000 flips | 5.45 × 10-9% |
| Chance a run of 43 appears at least once in 10,000 flips | 5.66 × 10-8% |
| Chance a run of 43 appears at least once in 100,000 flips | 5.68 × 10-7% |
Why it is likelier than it feels
A run of 43 on one chosen flip is 1 in 8.8 trillion, yet across 1,000 flips there is a 5.45 × 10-9% chance one turns up somewhere. People judge a streak against a single starting point, but a long sequence gives it thousands of starting points. That is also why streaks in a real record of flips look suspicious to anyone who does not expect them, and why a sequence with no streaks at all looks more made-up than one that has them.
Does a streak change the next flip?
No. After 43 heads the next flip is still 50% heads and 50% tails. A fair coin has no memory, and on Cryptoflip every game's result comes from a provably fair roll that was committed to before anyone joined. Expecting the streak to "break" is the gambler's fallacy, and expecting it to continue is the hot-hand fallacy.
In Original, our player-versus-player coin flip, a game is a straight 50/50 and the winner takes the pot minus a 5% fee. See how a result is verified.