About the Coin Flip Probability Calculator
Probability of getting exactly, at least or at most k heads in n coin tosses, for fair or biased coins.
Also known as: coin toss probability, heads or tails probability, coin probability, probability of heads.
How to use this calculator
- Enter flips, heads, p(heads).
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
P = C(n, k)·pᵏ·(1 − p)ⁿ⁻ᵏ
Worked example
Using the values pre-filled in the calculator above:
- Flips = 10
- Heads = 5
- P(heads) = 0.5
the calculator returns:
- P(exactly 5 heads): 0.24609375
- P(at most 5): 0.62304688
- P(at least 5): 0.62304688
- P(all heads): 0.00097656