Coin Flip

A virtual coin for quick decisions. Flip it once to get heads or tails, or flip thousands to watch the results settle toward half and half, which is a neat demonstration of probability.

How to use it

1. Set how many flips you want.
2. Press Flip.
3. Read the result.
4. Flip again for a new outcome.

When it helps

• Making a quick decision.
• Deciding who starts a game.
• Demonstrating probability in class.
• Settling a friendly dispute.

Good to know

• One flip gives one answer, many flips show the overall split.
• Ten flips are rarely exactly five and five; short runs vary more than people expect.
• For choosing between more than two options, use the Random Name Picker.

Is a virtual coin fair?

Yes. The result comes from the browser's cryptographic random generator, which gives heads and tails exactly equal chances. Real coins are very slightly biased, with research suggesting about a 51 percent chance of landing the way they started, but that doesn't apply here.

Each flip is independent. After five heads in a row, the next flip is still 50-50. The feeling that tails is due is a well-known mistake called the gambler's fallacy.

Worked example: watching probability settle

Flip 10 times and you might get 7 heads and 3 tails, a perfectly normal result. Flip 1,000 times and you'll typically land between 470 and 530 heads. The proportion gets closer to half as the number grows, even though the raw difference in counts can get bigger.

That behaviour is called the law of large numbers, and the tool makes it easy to see. Try flipping 100, then 1,000, then 10,000, and compare the percentages.

Using a coin flip to decide

A flip is good for settling minor choices where both options are acceptable. A popular trick is to notice how you feel while the coin is in the air: if you hope for a particular side, that tells you what you want, and you can ignore the coin.

For choosing among three or more options, use the Random Name Picker instead. For anything where fairness has real stakes, such as prizes, use a method everyone can watch.

A short history of flipping a coin

Deciding by coin toss goes back to ancient Rome, where the game was called "navia aut caput", meaning ship or head, after the images on the coins. It has settled everything from sporting kick-offs to the naming of the city of Portland, Oregon, in 1845.

Whatever the stakes, the logic is the same: when two options are equally acceptable, a random choice saves time and removes argument.

Flipping fairly with friends

If two people disagree, have one call heads or tails before the flip, so nobody can change their mind after seeing the result, and agree in advance that the outcome stands.

Questions