Coin Flip
Flip a virtual coin online. Heads or tails — instant random result with animation and flip history.
About this calculator
Flip one or many virtual coins and see heads or tails with a flip history.
A fair, instant way to settle a choice, and a small probability lab.
How to use it
- Choose the number of flips.
- Press Flip!
- Read the results and history.
The maths of coin flips
A fair coin lands heads with probability 1/2 on every flip, independent of earlier flips. In n flips, the expected number of heads is n/2, but the actual count varies: the standard deviation is √n/2. In 100 flips, heads between 40 and 60 happens about 95% of the time. The chance of a streak of at least k in a row grows with the number of flips: in 100 flips, a run of 6 or more of the same side is more likely than not.
Worked example
Probabilities
| Heads on one flip | 50% |
| Two heads in a row | 25% |
| Five heads in a row | 3.125% (1 in 32) |
| Ten heads in a row | about 0.098% (1 in 1,024) |
Tips and common mistakes
- Past flips do not affect the next one (the gambler's fallacy).
- Small samples vary a lot; 10 flips can easily be 7-3.
- Use 'best of 3' for fairness.
- Calling before the flip avoids disputes.
- Longer runs of the same side are normal in long sequences.
Frequently asked questions
Is the flip fair?
Yes, 50% each.
Is a streak of 5 heads unusual?
Not in many flips: 1 in 32 for any given 5.
Does the coin remember?
No, each flip is independent.
What is the gambler's fallacy?
Believing a streak makes the opposite more likely.
How many heads in 10 flips?
On average 5, but 3 to 7 is typical.
Is it free?
Yes.