Flip a Coin

Settle a choice, start a match or teach probability with a fair virtual coin. Flip once for a quick heads-or-tails answer, play best of three, five or seven, or flip up to 1,000 coins at once to watch the share of heads settle near 50%. Each flip is a separate unbiased draw from your browser's secure random generator.

How to use this tool

1. Enter how many coins to flip, or choose a best-of match.
2. Optionally add a seed if you need to repeat exactly the same flips later.
3. Press the button: the coin tosses and lands on the result.
4. Read the counts, the longest streak and how likely your split was.

Formula

P(exactly h heads in n flips) = C(n, h) ÷ 2ⁿ

C(n, h) is the number of ways to choose which h of the n flips are heads. The second probability adds up every outcome at least as far from an even split as yours, on both sides — the two-sided binomial test of a fair coin.

Example

In 10 flips with 7 heads, the chance of exactly that is C(10, 7) ÷ 1,024 = 120 ÷ 1,024 ≈ 11.72%. A split at least that uneven (0–3 or 7–10 heads) happens (1 + 10 + 45 + 120) × 2 ÷ 1,024 ≈ 34.38% of the time, so 7 heads is nothing unusual for a fair coin.