Flip a coin: heads or tails?
One click, one fair coin toss. Flip a coin once or 100 times and watch heads and tails creep towards 50%.
How it is calculated
Every flip is independent: heads and tails always have exactly 50%. The randomness comes from crypto.getRandomValues(), your browser's cryptographically secure random number generator. The result is fixed before the animation starts – when you click and how the coin spins change nothing.
How it works: a worked example with 10 coins
Set "Coins per flip" to 10 and the tool computes three numbers before every flip: expected heads = 10 ÷ 2 = 5 heads. Chance that all 10 coins land the same: 2 × (1/2)10 = 2/1024 ≈ 0.20%. Chance of exactly 5 heads and 5 tails: (10 choose 5) ÷ 210 = 252/1024 ≈ 24.61%. All three numbers sit right above the flip button and update the moment you change the count.
What the statistics show
After a few flips the share often strays far from 50% – 7 : 3 in ten flips is nothing unusual (chance of a deviation at least that large: about 34%). Only with many flips does the share settle near one half. That is the law of large numbers: the share becomes stable, while the absolute gap between heads and tails can still grow.
Streaks are normal
Many people find five heads in a row suspicious. In fact, in 100 flips a longest streak of 6 or 7 identical results is typical. Thinking "tails is due now" after a streak is the gambler's fallacy: the coin has no memory, the chance stays at 50%.
The values in the result box
- All the same: 2 × (1/2)n – 25% with 3 coins, only 0.2% with 10 coins.
- Exactly half: (n choose n/2) ÷ 2n – 24.61% with 10 coins, only 7.96% with 100 coins. An exact tie becomes less likely the more you flip.
Flip a coin 3 times or 10 times: the odds
The chance of exactly k heads in n flips is (n choose k) ÷ 2n. With 3 flips there are 23 = 8 equally likely sequences (HHH, HHT, HTH, …):
| Event | Math | Chance |
|---|---|---|
| 3 heads in a row | 1/8 | 12.5% |
| exactly 2 heads | 3/8 | 37.5% |
| at least 1 head | 1 − 1/8 = 7/8 | 87.5% |
| exactly 8 heads in 10 flips | 45/1024 | 4.39% |
| 10 heads in 10 flips | 1/1024 | 0.098% |
Flip a coin for yes or no
Decide before the flip what each side means, e.g. heads = yes, tails = no. A useful side effect: if you feel disappointed by the result, you usually know what you really wanted.
Famous coin flips
- Wright brothers, 1903: Wilbur won the coin toss for the first flight attempt; it failed, and three days later Orville flew.
- Portland, Oregon, 1845: the founders flipped a coin to decide whether the city would be named Boston or Portland.
- Euro 1968: the semi-final Italy vs. Soviet Union ended 0–0 after extra time – a coin toss sent Italy to the final.
Where the coin flip comes from and what it's used for
The idea is ancient: in Rome, people flipped coins in a practice called navia aut caput ("ship or head"), named after the images stamped on Roman coins. Today a coin flip decides kickoff and side selection in football (including the Super Bowl coin toss), splits teams for game night, or settles everyday disputes where both sides deserve equal odds.
A real coin can, in theory, also land on its edge, though it's extremely rare (rough estimate: about 1 in 6,000). This online flip only models the two faces, so it always gives a clear heads or tails.
More than two options? Use the dice roller or the wheel.
Frequently asked questions
Is a real coin really 50/50?
Almost. A study with more than 350,000 flips (Bartoš et al., 2023) found that a coin lands on the side it started on about 50.8% of the time. This online coin has no such bias: it is exactly 50/50.
Can I flip several coins at once?
Yes, choose 3, 5, 10 or 100 coins per flip. The statistics count every single coin.
Are my statistics saved?
No, they only live in this browser tab. "Reset statistics" or reloading the page starts over.
How often do five identical results in a row happen?
The chance that five given flips all match is 2 × (1/2)5 = 6.25%. Somewhere within 100 flips, though, a streak of at least five appears with about 97% probability.
Can a coin land on its edge?
A real coin can, though it's extremely rare (physicists estimate roughly 1 in 6,000 tosses). This online flip only models the two faces, so it always gives a clear heads or tails.
What is a coin flip used for in real life?
Common uses include the opening kickoff in football or the Super Bowl coin toss, splitting teams, settling everyday disputes, or any yes/no decision where both sides deserve equal odds.
What are the odds of 3 heads in a row?
(1/2)3 = 1/8 = 12.5%. At least one head in three flips, on the other hand, comes up 7/8 = 87.5% of the time. Pick "3 coins" above to try it.
Can a coin flip be rigged?
With a real coin, yes: practised flippers can influence the outcome with a consistent toss (Diaconis, Holmes & Montgomery, 2007). In this online flip, only your browser's cryptographic randomness decides, before the animation starts.
Sources and legal basis
- W3C Recommendation: W3C Web Cryptography API – getRandomValues()
- MDN Web Docs – Crypto.getRandomValues()
As of:
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