Or click the coin directly
Flip a coin to see your results here.
The Probability of Coin Flips
A fair coin lands heads 50% of the time on every flip, whatever came before, and the chance of 5 heads in a row is 1 in 32 (3.1%). Flip 1 to 10,000 virtual coins above and the tool counts heads, tails and your longest streak as you go.
A fair coin has exactly 50% probability for each side on every individual flip. Importantly, each flip is independent, previous results do not influence future ones. This is the gambler's fallacy: getting 10 heads in a row does not make tails "due" on the next flip.
Over a large number of flips, the law of large numbers ensures the ratio converges toward 50/50. Try flipping 10,000 coins to see this in action.
Independence
Streak Probability
Streak Odds at a Glance
The chance that a set of flips you pick in advance all come up heads (or all tails) halves with every extra flip.
| Heads in a row | Probability | About 1 in |
|---|---|---|
| 2 | 25% | 4 |
| 3 | 12.5% | 8 |
| 4 | 6.25% | 16 |
| 5 | 3.13% | 32 |
| 7 | 0.78% | 128 |
| 10 | 0.098% | 1,024 |
| 15 | 0.0031% | 32,768 |
| 20 | 0.0001% | 1,048,576 |
Streaks somewhere in a session are far more likely
Over many flips a long run turns up much more often than the table above suggests, because it can start anywhere. The "Longest Streak" stat above counts runs of either side.
| Flips | Run length | Chance of a heads run | Chance of a run of either side |
|---|---|---|---|
| 10 | 4 in a row | 24.5% | 46.5% |
| 100 | 6 in a row | 54.6% | 80.7% |
| 100 | 7 in a row | 31.7% | 54.2% |
| 1,000 | 8 in a row | 86.1% | 98.2% |
| 1,000 | 10 in a row | 38.5% | 62.4% |
The average longest run of either side is about 3.7 in 10 flips, 7.0 in 100, 10.3 in 1,000 and 13.6 in 10,000.
How Close to 50/50 Should You Expect?
Exactly half heads is less likely than most people think. What does shrink is the percentage gap.
| Flips | Exactly half heads | 95% of sessions land in |
|---|---|---|
| 10 | 24.6% | 2 to 8 heads |
| 100 | 7.96% | 40 to 60 heads |
| 1,000 | 2.52% | 469 to 531 heads |
| 10,000 | 0.80% | 4,902 to 5,098 heads |
So 58 heads out of 100 is normal, but 5,800 out of 10,000 would be a sign that something is off.
How This Coin Decides
Each flip calls Math.random(), the pseudorandom generator built into your browser, and counts it as heads when the number is below 0.5. That gives exactly even odds and is fine for games, classroom demos and deciding who does the dishes. It is not a cryptographic generator, so do not use it for a lottery, a paid prize draw or anything security related. Those need crypto.getRandomValues or a supervised draw. For passwords, use the password generator, which does use the crypto API.
The "Which Side Wins?" menu has two test settings that fix the result. Check it says Fair (50/50) before a real call.
Are real coins 50/50?
Very nearly. A 2023 study led by František Bartoš recorded 350,757 hand flips and found coins landed on the side they started on about 50.8% of the time, a small wobble bias. A virtual coin has no starting side, so it avoids that.