Flip 100 Coins at Once
One hundred flips at once, which makes the head count and the percentage the same number. You get the tally, the longest run, and the full sequence as copyable text.
Flip it
Each flip is an independent 50/50 draw from your browser's random number generator. A run of five or six the same way is normal in 100 flips — that is what surprises people most.
At this size the count is the percentage
Sixty heads out of a hundred is sixty per cent, with no arithmetic in between. That is the whole reason this batch size gets used in lessons and demonstrations.
Fifty-fifty is the top result and still uncommon
An exact 50-50 finish happens on fewer than one set in twelve. It is the most likely single count, and it is still the exception.
| Heads out of 100 | How often |
|---|---|
| Exactly 50 | 7.96% |
| 49 to 51 | 23.6% |
| 45 to 55 | 72.9% |
| 40 to 60 | 96.5% |
The standard deviation is exactly 5 heads, which is what makes 40 to 60 the near-certain band.
The longest run is usually six or seven
Across a hundred flips the longest streak averages 7.0. Six is the most common answer at 26.4%, seven next at 22.8%. A streak of seven or more shows up in 54.2% of sets, and a streak of five or more is close to guaranteed at 97.2%. Under four is almost impossible: it happens in 3 sets in 10,000.
It does not correct itself
A hundred flips contain about 50 separate runs, because each flip has an even chance of matching the one before it. After six heads the seventh flip is still 50/50; nothing is owed and nothing is due. See heads or tails for the single-toss version, fifty flips for a smaller sample, or a thousand flips to watch the percentage settle down.