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Coin Flip Online: Heads or Tails, With Streak Odds
Quick answer
Press Flip for one coin toss: heads or tails, each with exactly a 50% chance. Use the 10, 100 or 1,000 buttons to flip many coins at once and see the running totals and your longest streak. Each flip is independent, so previous results never change the next one.
| Chance of heads | Exactly 50% |
|---|---|
| Chance of 5 heads in a row | 1 in 32 (3.13%) |
| Chance of 10 heads in a row | 1 in 1,024 (0.098%) |
| Longest streak in 100 flips | 5 to 7 in a row about two times in three |
| Randomness | crypto.getRandomValues in your browser |
Flip a coin online for a quick heads or tails. Press Flip for one toss, or flip 10, 100 or 1,000 coins at once to see how real randomness behaves: the split drifts around 50/50, and streaks are longer than most people expect.
Flip a coin
Is an online coin flip fair?
Each flip uses one random bit from crypto.getRandomValues, the cryptographically secure generator built into your browser. A bit is 0 or 1 with exactly equal chance, so heads and tails are exactly 50/50, and no flip depends on the one before.
Real coins are close to fair but not perfect. In a large study, published as a preprint in 2023, researchers flipped coins 350,757 times and found they landed on the side that started facing up about 51% of the time. Over a handful of flips you would never notice; over hundreds of thousands, it shows.
Odds of a streak
The chance of a particular run of heads (or tails) halves with every extra flip:
| In a row | Chance (one particular side) | 1 in |
|---|---|---|
| 2 | 25% | 4 |
| 3 | 12.5% | 8 |
| 5 | 3.13% | 32 |
| 7 | 0.78% | 128 |
| 10 | 0.098% | 1,024 |
P(n in a row) = (1/2)ⁿ5 heads in a row: (1/2)⁵ = 1/32 ≈ 3.13%. Either side 5 in a row: 2 × 1/32 = 1/16 = 6.25%.
That table is for a streak starting right now. Over a long session, streaks are much more common, because they can start at any point. We worked out the exact odds for 100 flips: a run of at least 5 of the same side turns up in about 97% of sequences, at least 6 in about 81%, and at least 7 in about 54%. Try Flip 100 a few times and you'll see it.
Heads or tails? Good uses for a coin flip
- Two-way decisions: who starts, which film, left or right.
- Settling ties in games and quizzes.
- Teaching probability: flip 1,000 coins and watch the percentage settle near 50% while the raw difference between heads and tails still wanders.
For more than two options, use the spin-the-wheel picker or the random number generator.
Coin flips and the gambler's fallacy
After five tails, it feels as if heads is "due". It isn't: the next flip is still 50/50. Britannica calls this belief the doctrine of the maturity of the chances, and it's the idea behind most doomed betting systems. Our martingale calculator shows what happens when you double your bet after every loss on an even-money bet.
Frequently asked questions
Is a coin flip really 50/50?
This one is: each flip takes one random bit from your browser's cryptographic generator, so heads and tails each have exactly a 50% chance. Real coins come very close too. Researchers who studied hundreds of thousands of real tosses found a small bias toward landing on the same side that started facing up, around 51%.
What are the odds of getting heads 3 times in a row?
1 in 8, or 12.5%. Each flip is 1 in 2, and you multiply: 1/2 × 1/2 × 1/2 = 1/8. For 5 in a row it's 1 in 32, and for 10 in a row it's 1 in 1,024.
After 5 tails in a row, is heads more likely?
No. The coin has no memory, so the next flip is still exactly 50/50. Expecting a correction is the gambler's fallacy.
How long a streak should I expect in 100 flips?
In 100 fair flips, the longest run of the same side is 5, 6 or 7 about two times in three. About 81% of 100-flip sequences contain a streak of at least 6 of the same side, and about 31% contain 8 or more, so long runs are normal.
Sources
- Crypto: getRandomValues() method — MDN Web Docs
- Fair coins tend to land on the same side they started: Evidence from 350,757 flips — Bartoš et al., arXiv
- Doctrine of the maturity of the chances — Encyclopaedia Britannica. Gambler's fallacy: falsely assumes plays are dependent