How to use the Coin Flip
- Press the Flip the Coin button or tap the coin. It spins in the air and lands on heads (H) or tails (T).
- Before you flip, agree on what each side means, for example "heads means A, tails means B."
- The stats below show how many heads and tails you've had so far, the percentage of each, and how many times in a row the same side has come up.
- To experiment with probability, use Flip many times at once to flip anywhere from 10 to 10,000 times and compare the ratios.
Is a coin flip really 50/50?
In theory, a fair coin lands on heads or tails with a probability of 1/2 each, or 50%. Real coins can have tiny biases depending on weight distribution and how they're tossed, but Tooljip's online coin uses your browser's cryptographic random number generator (crypto.getRandomValues) to pick 0 or 1, so the odds are exactly 50%.
That said, 50% means "the ratio gets close to half over a very large number of flips." It doesn't mean 10 flips will give you 5 of each. The chance of getting exactly 5 heads in 10 flips is only about 24.6%. Compare 10, 1,000 and 10,000 flips with the batch buttons and you can watch the law of large numbers in action: the more you flip, the closer the ratio gets to 50%.
Because everything runs in your browser, there's nothing to install and no account to create. The tool works the same on phones, tablets and computers.
Five heads in a row: is tails due next? (The gambler's fallacy)
After a run of heads, many people feel that tails is "due." But a coin has no memory of earlier results. No matter how many heads in a row you've had, the chance of heads on the next flip is still 50%. This mistake is known as the gambler's fallacy.
Long streaks actually happen more often than most people expect. Here's the probability of seeing a streak of the same side at least once in 100 flips:
| Same side in a row | Chance of it happening at least once in 100 flips |
|---|---|
| 5 or more | About 97% |
| 6 or more | About 81% |
| 7 or more | About 54% |
So a streak of the same side doesn't mean the coin is broken. It's a perfectly normal part of randomness.
Good times to settle things with a coin flip
- Kickoff, serve or ends in sports: the coin toss before an American football or soccer game, the toss in cricket, or picking who serves first in volleyball or table tennis.
- Torn between two options: pizza or tacos, a movie or a walk? When both are fine, let the coin decide. If you feel a twinge of disappointment at the result, that may be a sign you really wanted the other option.
- Turn order in games: deciding which of two players goes first in a board game, card game or video game.
- Friendly disputes: who does the dishes, who picks the playlist, or who rides in the front seat.
If you have three or more options, try the spinning wheel or the dice roller. If two people want to compete for it, use rock paper scissors.