Coin flipper

A coin flip is the simplest fair way to settle a two-way choice: who goes first, which option to try, or which team kicks off. This virtual coin gives heads or tails with an equal 50% chance and keeps a tally so you can see the results of many flips.

How to use it

1. Click to flip.
2. Read the result and the running count of heads and tails.
3. Flip several times for best-of-three or best-of-five decisions.

Is it really random?

The result is drawn from the browser's cryptographically secure random number generator, crypto.getRandomValues, which is suitable even for security purposes. Each flip is independent: after five heads in a row, the next flip is still exactly 50/50. Believing that tails is now due is a well-known mistake called the gambler's fallacy.

What to expect over many flips

Over 10 flips, getting 7 heads and 3 tails is not unusual; it happens about 12% of the time. Over 1,000 flips the proportion of heads will usually be between 47% and 53%. Streaks are normal too: in 100 flips you will very likely see a run of 6 or more of the same side.

Fun facts

• Real coins are not perfectly fair. Research by Persi Diaconis showed a hand-flipped coin lands on the side it started on slightly more than half the time, about 51%.
• A spun coin, rather than a flipped one, can be strongly biased by its weight distribution.