Calculates the probability of flipping a fair coin and getting the same result a specific number of times in a row.
How it works
Since each flip is independent with a 50% chance, the probability of N consecutive matching flips is one-half raised to the power of N.
What this does not include
This does not include the probability of exactly k heads across n flips in any order — for that different question, use this site’s coin flip probability calculator instead.
How to use this calculator
- Enter the streak length you want the probability for.
A worked example
The probability of flipping the same result 3 times in a row: (½)³ × 100 = 12.5%.
5 in a row: (½)⁵ × 100 = 3.125% — each additional flip in the streak roughly halves the probability.
What the variables mean
| Variable | Meaning |
|---|---|
| Streak length | How many consecutive identical results are being asked about |
Edge cases worth knowing
Each extra flip in the streak cuts the probability roughly in half — a direct consequence of each flip being an independent 50/50 event, so the probabilities multiply rather than add.
A streak length of zero has no meaningful probability — there’s no sequence of flips to evaluate, so the calculator declines to show a result.
Frequently asked questions
Why does the probability shrink so fast with a longer streak?
Because each additional flip multiplies the probability by another one-half — the chance drops exponentially, not linearly, as the streak grows.
Does a long streak mean the coin is unfair?
Not necessarily — even fair coins produce long streaks occasionally; over many flips, streaks of various lengths are statistically expected to occur.
Is this the same as “gambler’s fallacy” thinking?
No — this calculates the probability of a streak happening in the first place. It does not imply that after a streak, the next flip is “due” to break it — each flip remains independently 50/50.
