Coin Flipper: Flip 1 to 100 Coins, Heads or Tails

About the Coin Flipper

The Coin Flipper tosses one coin or up to a hundred coins at once and keeps score. Every coin lands on heads or tails with exactly the same chance, and the result is animated so it feels like a real toss. Use it to settle a decision, to pick who goes first in a game, or to see for yourself how heads and tails behave over many flips. A running tally shows the number of heads and tails and their percentages, and a history lists your last 50 flips with the newest first.

The flips come from your browser's cryptographic random generator (crypto.getRandomValues). Each coin takes one random byte and reads its lowest bit: 1 means heads and 0 means tails. Because every byte value from 0 to 255 is equally likely and exactly half of them are odd, the odds are an exact 50 to 50. Nothing is predictable and nothing is repeated from a seed.

How to flip a coin

The maths of a fair coin

The chance of exactly $k$ heads in $n$ fair flips is

$$P(k) = \binom{n}{k} \left(\frac{1}{2}\right)^{n}$$

With two coins there are four equally likely outcomes, so one head and one tail turn up half of the time, while two heads or two tails each turn up a quarter of the time. For ten coins, exactly five heads has a chance of about 24.6 percent, which is the single most likely outcome and still happens less than a quarter of the time.

Worked examples

• Single flip: one coin gives heads or tails with a chance of 50 percent each, whatever came before.
• Streaks: the chance of five heads in a row is $(1/2)^5 = 1/32$, about 3.1 percent. Over a long session you will see such streaks, and they do not mean the coin is broken.
• The law of large numbers: after 10 flips you might see 7 heads (70 percent). After 1000 flips the share of heads settles close to 50 percent, usually within a few points, although the raw difference between heads and tails can still grow.

Common uses

• Deciding between two options when you cannot choose.
• Choosing who starts a game or takes the first turn.
• Teaching probability with a large number of tosses in a classroom.
• Settling a friendly bet without a real coin to hand.

Privacy

Nothing is uploaded; every calculation runs in your browser and never leaves your device. The tally and the history live only on this page and disappear when you close or reload it.

Related tools

Need a number rather than a side? Use the Random Number Generator for dice and lots. The Number List Calculator sums and averages the numbers you collect, and the Password Generator uses the same cryptographic random source for secrets.

Frequently asked questions