Coin Flip Probability Calculator

About this calculator

This calculator applies the binomial probability formula, P(k) = C(n,k) × 0.5ⁿ, to find the chance of getting exactly k heads in n flips of a fair coin, where C(n,k) is the number of ways to choose which k of the n flips land heads (n choose k) and 0.5ⁿ accounts for every flip having a 50/50 chance independent of the others.

It also reports the probability of any one specific exact sequence of heads and tails, which is always simply 0.5ⁿ regardless of how many heads it contains — a distinction that trips people up, since a specific sequence like HHHHH feels rarer than “3 heads out of 5” even though both are governed by the same binomial math underneath. It's a clean, hands-on introduction to discrete probability and combinatorics.