Flip 20 Coins at Once
One press runs 20 flips and reports the sequence, the running tally and the longest streak. A dead-even 10-10 is the most likely total and arrives only 17.6% of the time.
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.
20 flips, over a million sequences
There are 1,048,576 possible sequences and each is equally likely. Exactly 10 heads is the single most common total at 17.6%, which means 82.4% of runs do not split cleanly down the middle.
The band matters more than the peak. Between 8 and 12 heads covers 73.7% of runs, and 6 to 14 heads covers 95.9%. A total of 15 or more on one side happens in 4.1% of runs, and 16 or more in 1.2%. That is the honest answer to how lopsided is too lopsided: 20 flips is far too short a run to catch a biased coin.
The longest run you should expect
Over 20 flips the longest streak averages 4.7. Five or more in a row appear in 45.8% of runs, six or more in 23.7%, and three or more in 97.9%. If your 20 flips contain a run of five, that is the ordinary outcome.
A coin has no memory
After 15 heads out of 20, the next flip is still 50/50. Nothing is owed and tails is not due. Long-run ratios settle toward half only because later flips outnumber an early gap, never because the coin corrects for it. In absolute numbers the gap between heads and tails tends to widen, not close.
Other counts
Fewer flips at 10 at a time, many more at 50 at a time, and any count you like on the coin flip page.