Coin Flip
Flip a virtual coin for a quick heads-or-tails decision, or flip up to 1,000 at once to see how counts, percentages and streaks behave. Running totals and the longest streak are kept until you reset. Free, no sign-up, and nothing leaves your browser.
Flip many at once
Every flip is one unbiased bit from your browser's cryptographic random source: an exact 50% chance of heads and 50% chance of tails, and no flip is influenced by the ones before it.
How to Use the Coin Flip
- 1. Flip once to decide. Press Flip Coin. The coin spins for about half a second and lands on heads or tails; the result is added to your running tally.
- 2. Flip many to see the pattern. Enter a number from 1 to 1,000 under Flip many at once and press the button. You get that batch's heads and tails counts with percentages, and the batch is added to your totals.
- 3. Read the tally. After the first flip, four cards show total flips, heads, tails and the longest streak — the longest unbroken run of one side since you last reset.
- 4. Reset to clear the totals and the streak and start a fresh experiment.
What to Expect From a Fair Coin
Every flip is independent: whatever came before, the next flip is 50/50. Three heads in a row does not make tails "due" — that belief is the gambler's fallacy. What does settle down is the proportion, not the difference. As flips accumulate, the share of heads closes in on 50%, while the raw gap between heads and tails typically keeps growing. The spread is easy to quantify: the number of heads in n fair flips has a standard deviation of √n / 2.
| Flips | Typical spread (1 SD) | Chance heads falls in the range | What it means |
|---|---|---|---|
| 10 | ±1.6 heads | 34.4% chance of a 7–3 split or worse (either way) | Lopsided results are normal in small samples. |
| 100 | ±5 heads | 96.5% for 40–60 heads | Exactly 50 heads happens only 8.0% of the time. |
| 1,000 | ±15.8 heads | 94.6% for 470–530 heads (47–53%) | Percentages are tight, though the gap is often 20 or more flips. |
Streaks Are Longer Than You Think
The longest-streak card exists because people underestimate runs. In 20 flips there is a 45.8% chance of a run of five or more of the same side. In 100 flips the chance of a run of at least six is 80.7%, and of at least seven, 54.2%. In 1,000 flips a run of ten or more turns up 62.4% of the time. A batch of 100 with a longest streak of 6 to 8 is therefore completely ordinary; a batch with no streak longer than 3 would be the surprising one. (The streak counts across single flips and batches until you reset.)
How the Flips Are Made
Each flip is one unbiased bit from your browser's cryptographic random source (crypto.getRandomValues): the shared generator draws a whole number below 2 with rejection sampling, and 0 is heads while 1 is tails. Two outcomes divide the generator's range evenly, so there is no scaling or rounding to introduce bias, and no flip depends on the one before. Use it for classroom demonstrations, games and everyday decisions. The outcome of a single flip is decided when you press the button; the spin is decoration, and the batch and reset buttons wait until the coin has landed so the running tally and streaks never lose a flip.
A real coin is not exactly 50/50
Diaconis, Holmes and Montgomery (2007) showed from the physics of a spinning coin that a normal toss favors the side that started facing up, by roughly 51%. A preregistered study of 350,757 flips by Bartoš and colleagues (Journal of the American Statistical Association, 2025) measured 50.8%. A virtual coin has no starting side, so this one is not affected.
Which Tool Do You Need?
| If you want… | Use |
|---|---|
| Two outcomes, with a tally and streaks | This Coin Flip |
| Six, twenty or a hundred outcomes, or a sum of several dice | Dice Roller |
| Two or more named options, with a spinning wheel | Wheel Spinner |
| Numbers from a range, such as 1 or 2 | Random Number Generator |
| Cards dealt from a shuffled deck | Random Card Draw |
| The chance of getting k heads in n flips | Binomial Distribution Calculator |
Frequently Asked Questions
- How do I flip a coin online?
- Press Flip Coin. The coin spins and lands on heads or tails, and the result is added to the tally. The result is chosen at the moment you press the button; the animation only shows it.
- Is the coin flip really 50/50?
- Yes, in the sense that matters here: the tool draws one unbiased bit from your browser's cryptographic random source and calls it heads or tails, so each side has exactly the same chance, and no flip depends on the one before. Like all computer-generated randomness it is not a physical process, but the result cannot be predicted from earlier flips.
- Why are my heads and tails percentages not exactly 50%?
- Because randomness varies. Ten fair flips give a 7–3 split or worse about 34% of the time, and even 100 flips land on exactly 50 heads only 8% of the time. The percentages converge toward 50% as the number of flips grows, which is the law of large numbers, but the raw gap between heads and tails tends to widen.
- What does the longest streak show?
- The longest unbroken run of the same side since your last reset, counted across single flips and batches together. Long streaks are expected: a run of six or more appears in 100 flips about four times out of five.
- How many coins can I flip at once?
- Up to 1,000 per batch. The batch shows its heads and tails counts with percentages and is added to your running totals. Individual results are not listed, because the point of a large batch is the counts.
- Is a coin flip fair for settling a decision?
- For two options, yes — every flip is equally likely to land either way. Agree on which side means what before you press the button, and flip once; repeating until you get the answer you wanted defeats the point.