Flip a Coin Online: Heads or Tails (Fair 50/50)

How the flip is generated

Each flip calls the browser's crypto.getRandomValues function, the same cryptographically secure generator used to create encryption keys and session tokens. It is seeded from hardware and operating system entropy, so results cannot be predicted from earlier flips. The number it returns is reduced to 0 or 1, tails or heads, with an equal chance of each.

Flips are independent. The coin has no memory: after five heads in a row, the next flip is still exactly 50/50. Believing tails is now 'due' is the gambler's fallacy, and it has emptied a lot of wallets at roulette tables.

The math of streaks and splits

The chance of a specific sequence of n flips is (1/2)^n. Five heads in a row: 1 in 32, about 3.1 percent. Ten in a row: 1 in 1,024. That sounds rare, but in a long run of flips, streaks are normal. In 100 flips, a streak of at least six of the same side shows up about 80 percent of the time.

Exact 50/50 splits are less common than people expect. In 10 flips, exactly 5 heads happens only 24.6 percent of the time, calculated as 252 ways out of 1,024. In 100 flips, getting between 40 and 60 heads happens about 96 percent of the time, and exactly 50 only about 8 percent.

Watch the law of large numbers

Flip 10 coins and you might see 70 percent heads. Flip 100,000 and the result will almost certainly land within half a percentage point of 50 percent. The percentage converges toward 50 even though the raw difference between heads and tails usually grows in absolute terms. That is the law of large numbers: averages stabilize, individual outcomes don't.

Try it: flip 10, then 1,000, then 100,000 and compare the percentages in the tally. It is a quick classroom demonstration of why casinos, insurers, and polling firms can predict totals with confidence while individual outcomes stay uncertain.

Are real coins fair?

Almost. A 2023 study by František Bartoš and colleagues recorded 350,757 flips by 48 people and found coins landed on the same side they started on about 50.8 percent of the time. The cause is precession: a flipped coin wobbles as it spins and spends slightly more time with its starting face up. The bias is tiny, but it means a human flip where the flipper can see the starting side is not perfectly fair.

Spinning a coin on a table is worse. The weight difference between the two faces can push results well away from 50/50 for some coins. A digital flip has no starting side and no physics, so it avoids both problems.

Good uses for a coin flip

Settling a tie: who goes first in a game, who takes the first shift, which of two equal options to pick. Sports use it too: every NFL game begins with a coin toss to decide who receives the kickoff. For more than two options, use the dice roller or random name picker.

A coin flip also helps with indecision in a subtler way. Assign each option to a side and flip. If you feel relief at the result, go with it. If you feel disappointment, you just learned you wanted the other option. Either way, the coin made the decision clearer.

Using this tool

Press Flip coin for a single result, or set a number up to 100,000 and press Flip all for a batch. The tally tracks heads, tails, totals, and percentages across every flip until you reset it. Nothing is sent to a server; every flip happens in your browser.

For a fair decision between two people, agree on who calls which side before anyone presses the button, and decide in advance whether it is one flip or best of three. Changing the rules after seeing a result is the only way to make a fair coin unfair.