Coin Flip
Flip a fair coin, or a hundred, and see heads, tails and the longest streak.
Good to know. If you’re secretly hoping for heads while the coin is in the air, you already know your answer.
How it works
In plain words
Each coin is heads or tails with an equal chance of 1 in 2, drawn from a seeded random number generator. Every flip is independent of the ones before.
The formula
P(heads) = P(tails) = 1/2 P(n heads in a row) = (1/2)ⁿ
Worked example
Ten coins flipped with the seed “example” came out as 6 heads, 4 tails. Press “Flip again” for a fresh set.
Sources
- Bartoš et al., Fair coins tend to land on the same side they started: evidence from 350,757 flips, 2023 The 51% same-side bias of real coins.
Sources checked September 30, 2026. 4 automated tests check its answers on every change.
About the coin flip
Flip a coin to settle a decision, pick who goes first, or start a game. Press “Flip again” for another toss. Choose more coins to flip many at once, and the calculator counts heads and tails, the share of heads and the longest run of the same side.
Each flip has an equal chance of heads or tails, and the coin has no memory: after five heads in a row, the next flip is still 50/50. Streaks are more common than most people expect. In 100 flips, a run of six or seven of the same side is normal, and 50 heads exactly happens only about 8% of the time. Flip 100 a few times to see it.
The result comes from a seeded pseudo-random generator, fair for everyday use. The seed is saved in the share link, so anyone you send it to sees the same flip, which makes it easy to prove the result. It is not suitable for gambling or security.
Real coins are nearly fair too. A 2023 study of 350,000 flips found a coin lands on the side it started on about 51% of the time, a tiny bias that a virtual coin doesn’t have.
Questions people ask
Is a coin flip really 50/50?
This one is. Real coins land on the side they started on about 51% of the time, a tiny bias.
What are the odds of 5 heads in a row?
1 in 32: (1/2)⁵. For 10 in a row, 1 in 1,024.
Can I share the result?
Yes. The link includes the seed, so the person you send it to sees the same flip.