Calculate probabilities of consecutive outcomes in a series of coin flips.
Last updated: March 2026
A streak is a sequence of consecutive identical outcomes. In coin flipping, a streak of 5 heads means getting HHHHH in a row. People often underestimate how likely streaks are—this is known as the "hot hand fallacy" or gambler's fallacy.
Contrary to intuition, streaks occur surprisingly often in random sequences. In 100 fair coin flips, there's approximately a 97% probability of observing at least one streak of 5 consecutive heads somewhere in the sequence. This demonstrates why randomness often feels "non-random" to our brains.
This calculator helps quantify streak probabilities, which is essential for understanding random processes in sports analytics, quality control, medical testing, and financial markets.
Flip a fair coin 100 times. How likely is a streak of 5 heads?
Our brains expect randomness to look 'random,' but true randomness includes streaks. We notice streaks and remember them (confirmation bias), making them seem less random than they are.
No, streaks are expected in fair random sequences. You need statistical tests (like chi-square) to determine if a coin is actually biased. One streak proves nothing.
It's the average number of flips you'd need to observe before seeing your first streak of the desired length. For a streak of 5 heads, expect roughly ~62 flips on average.
Lower p makes long streaks rarer (exponentially rarer). A streak of 5 heads (p=0.5) is more likely than a streak of 5 tails with a biased coin (p=0.7).
This calculator computes probabilities analytically, instantly giving exact answers. Simulation requires many iterations and only gives approximations.
Yes! Any binary outcome (win/loss, up/down) with consistent success probability. Just set p to your empirical success rate and n to your time period.
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