Quick Answer: In 100 fair coin flips, you expect 50 heads. However, results between 40 and 60 heads are completely normal (about 95% of all 100-flip experiments fall in this range). Getting exactly 50 heads has only a ~8% probability.
The Statistics of 100 Flips
For 100 fair coin flips, the number of heads follows a Binomial Distribution with parameters n=100 and p=0.5. The key statistics are:
| Statistic | Value | Meaning |
|---|---|---|
| Expected heads | 50 | Most likely individual outcome |
| Standard deviation | 5 | Typical deviation from 50 |
| 95% interval | 40–60 heads | 95% of experiments fall here |
| P(exactly 50) | ~7.96% | Getting exactly 50 is uncommon |
| P(60+ heads) | ~2.8% | Possible but unusual |
| P(35 or fewer) | ~0.7% | Very unusual but not impossible |
What to Expect in a Real 100-Flip Experiment
In a real 100-flip experiment, getting exactly 50 heads is actually less likely than getting 49 or 51. The most likely outcome is somewhere between 45-55. Results between 40-60 are completely ordinary. Results outside 40-60 (fewer than 40 or more than 60 heads) are statistically unusual but possible in about 5% of experiments.
Expected Streaks in 100 Flips
- Expected longest streak: approximately 6-7 consecutive identical results
- Probability of at least one streak of 6: >90%
- Probability of at least one streak of 8: ~50%
- Probability of at least one streak of 10: ~25%
Try It Yourself
Use PickRandom.online's Coin Flip to run a sequence experiment. Flip 100 times, record the results, and see how they compare to these statistical expectations. This is an excellent illustration of the Law of Large Numbers and the natural variability of random processes.