Work out coin flip probability instantly with clear inputs, formula shown and shareable results.
Flips follow the binomial distribution: the chance of exactly k heads is C(n, k) p^k (1 - p)^(n - k), and the cumulative tail sums that from k upwards. Seven heads in ten looks unusual but happens about 12% of the time with a fair coin, which is why short streaks are poor evidence of bias.
Binomial probability
P(exactly k) = C(n, k) x p^k x (1 - p)^(n - k)
Expected heads
expected = flips x chance of heads
P(exactly k) = C(n, k) x p^k x (1 - p)^(n - k). Flips follow the binomial distribution: the chance of exactly k heads is C(n, k) p^k (1 - p)^(n - k), and the cumulative tail sums that from k upwards.
Seven heads in ten looks unusual but happens about 12% of the time with a fair coin, which is why short streaks are poor evidence of bias.
Enter number of flips, heads you are asking about, chance of heads on one flip. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.