CoinFlipSim

Flip a Coin 100 Times — See Probability in Action

Run a hundred flips in one click and watch the split converge toward 50/50.

Press the button to run 100 flips

One hundred flips, one click

Flipping a real coin a hundred times takes the better part of ten patient minutes and a very cooperative floor. This page compresses the whole experiment into a single click: press the button and one hundred cryptographically random flips are generated instantly, tallied, and laid out for inspection.

The results panel shows the heads and tails counts with a percentage bar and the complete sequence of one hundred outcomes. You will almost always land within a few flips of 50–50 — a 60–40 result or wider happens less than one run in twenty — which is a dramatic tightening compared with ten-flip batches.

The law of large numbers, visible

A hundred flips is the classic classroom demonstration of the law of large numbers: as the sample grows, the share of heads converges on the true probability of 50%. A ten-flip batch might swing to 70%; a hundred-flip batch almost never does. Doubling the flips does not double the expected deviation — it shrinks it, proportionally.

Teachers use exactly this experiment because the numbers are big enough to be convincing and small enough to count by hand if anyone doubts the machine. Run the batch several times and compare: each run lands near half, but almost never exactly on it — and never in the same place twice.

Streaks still happen

Do not be surprised to find a run of six or seven identical results inside your hundred flips — such streaks are not just possible but expected somewhere in a sample this size. Randomness is lumpy, not alternating, and the sequence view makes those lumps easy to spot.

Your run history is kept locally in the browser, so you can repeat the experiment across visits and accumulate your own personal dataset of hundreds of flips, all feeding the site-wide statistics dashboard.

Frequently Asked Questions

＋How close to 50/50 will 100 coin flips be?

Usually within about five flips of 50–50. The chance of ending exactly 50–50 is only about 8%, but results outside the 40–60 range are uncommon — roughly one run in twenty.

＋What is the chance of 100 heads in a row?

Effectively zero for practical purposes: about 1 in 1.27 nonillion (10^30). No one in history has ever flipped 100 consecutive heads, real or virtual.

＋Can I use this for a classroom probability lesson?

Yes — this page is built for exactly that. Students can run the batch themselves, count the streaks in the sequence, and compare their result with classmates to see how the law of large numbers tames randomness.