Coin Toss Streak Calculator: Probability of Consecutive Heads or Tails

Your details

How many consecutive identical outcomes (heads or tails) you want to observe.
in a row
Total number of coin flips in your experiment or game.
tosses
Whether you are targeting a run of heads, a run of tails, or a run of any consistent outcome.
For a fair coin use 0.5. For a weighted coin enter the known probability of heads per toss.
Probability of at least one streakLikely
90.34%

Chance of seeing your target streak at least once in the given number of tosses

Expected tosses to first streak62tosses
Single-run probability3.125%
Probability of no streak9.66%
90.34% %
Rare<10Unlikely10-40Possible40-75Likely75-99Near-certain99+

90.3% chance of 5 heads in a row within 100 tosses

  • With 100 tosses there is a 90.3% chance of seeing at least one run of 5 heads in a row.
  • On average you would need to flip the coin 62 times before the first such streak appears.
  • Any particular block of 5 consecutive tosses has only a 3.1250% chance of being all the target outcome, but with 100 tosses there are many overlapping windows.

Next stepAdjust the streak length or total tosses to explore how sensitive the probability is to each parameter.

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