Rock paper scissors

The rules

If both players pick the same move it is a tie, and you play again.

Can you win every time

The computer picks its move with your browser's cryptographic generator, without seeing yours and without any habit to spot. Whatever your strategy, you have a one in three chance to win, one in three to lose and one in three to tie.

\[ P(\text{win}) = P(\text{loss}) = P(\text{tie}) = \dfrac{1}{3} \approx 33.3\% \]

Against a person it is different: beginners often open with rock, which makes paper a good first move.

Game modes

• Free play: play forever, the score keeps adding up.
• Best of 3: first to 2 wins takes the match.
• Best of 5: first to 3 wins takes the match.

Your best win streak is saved on this device.

Rock paper scissors: the odds

In rock paper scissors, every move loses to another. So no move is better than the other two.

If your opponent plays at random, you have a 1 in 3 chance to win, 1 in 3 to tie and 1 in 3 to lose. Over 90 rounds, then, you win about 30.

In game theory, the best play is therefore to pick each move at random with probability 1/3.

Rock paper scissors: reading a human opponent

People rarely play perfectly at random. For example, many players switch moves after a loss, or avoid repeating the same move twice.

Also, those habits can be spotted. If a player loses with rock, they often pick something else next. You can then predict the next move.

However, a good player knows they are being read. The safest habit is to mix things up with no fixed pattern. Against the computer in this tool, which plays at random, no reading works at all.

Pick a match format

A single round settles a quick argument. A longer series, however, reduces the role of luck.

• In a best-of-3, the first to 2 rounds wins.
• In a best-of-5, you need 3 rounds.
• In a best-of-7, you need 4 rounds.

Next, compare with other ways to decide. For two options, a coin flip is faster. For a group, try the random name picker or the wheel spinner.

Rock paper scissors: origins and variants

The game of rock paper scissors has existed for centuries in Asia, in similar forms. Today, people play it everywhere, from school yards to official tournaments.

There are also versions with more moves. For example, rock paper scissors lizard Spock has five moves, and each one beats two others.

In both cases, though, a tie is still possible. So play several rounds to get a clear winner.

Rock paper scissors: settling an argument

The game works well for settling a small disagreement. For example, two brothers decide who gets the remote.

To make the decision stick, follow three rules. First, play both moves at the same time, without waiting for the other player. Next, announce the number of rounds before you begin. Finally, accept the result, even if you dislike it.

If you play from a distance, the tool plays for you against the computer and rules out cheating. So you just click and let chance answer.

Rock paper scissors: tips for beginners

You cannot beat chance, but you can dodge the traps. First, change your move without following a fixed rule. Next, do not always replay the move that just won. Finally, mix short and long streaks.

For example, against a friend, watch their first move over three games. If you spot a habit, you can use it. Against the computer, though, play whatever you like: the odds do not move.