Rock Paper Scissors
Play rock paper scissors against a computer that picks at random, with a scoreboard, win rate and streaks. Every round is 1 in 3 to win, lose or draw. How it works
Use the Rock Paper Scissors
Choose Your Move
Pick a move to play the first round.
Rounds: 0 · Win rate: none yet
Recent Rounds
About the Rock Paper Scissors
Each round is a 1 in 3 chance to win, 1 in 3 to lose and 1 in 3 to draw, whatever you play. The computer picks Rock, Paper or Scissors with equal odds from the browser’s cryptographic random generator and never looks at your earlier moves, so no strategy beats it over many rounds.
Who wins each pairing
| You play | Computer plays Rock | Computer plays Paper | Computer plays Scissors |
|---|---|---|---|
| Rock | Draw | Loss | Win |
| Paper | Win | Draw | Loss |
| Scissors | Loss | Win | Draw |
Every row holds one win, one loss and one draw, and each column comes up one round in three, so every move has the same chances.
Chance of the same result several rounds in a row
| Rounds in a row | Chance | About 1 in |
|---|---|---|
| 1 | 33.3% | 3 |
| 2 | 11.1% | 9 |
| 3 | 3.70% | 27 |
| 4 | 1.23% | 81 |
| 5 | 0.412% | 243 |
| 6 | 0.137% | 729 |
| 7 | 0.0457% | 2,187 |
| 8 | 0.0152% | 6,561 |
| 9 | 0.00508% | 19,683 |
| 10 | 0.00169% | 59,049 |
The chance that your next k rounds are all wins is (1/3)^k. All losses or all draws have the same chance.
Expected results over many rounds
| Rounds | Wins | Losses | Draws | Win rate |
|---|---|---|---|---|
| 30 | 10 | 10 | 10 | 33.3% |
| 90 | 30 | 30 | 30 | 33.3% |
| 300 | 100 | 100 | 100 | 33.3% |
| 3,000 | 1,000 | 1,000 | 1,000 | 33.3% |
Averages. Real runs spread around them, and short runs spread the most. The win rate counts draws as rounds.
Frequently asked questions
- Can you beat the computer at rock paper scissors?
- In one round, one time in three. Over many rounds, no: its move is random and does not depend on yours, so over 300 rounds you can expect about 100 wins, 100 losses and 100 draws, whatever pattern you play.
- What is the best move in rock paper scissors?
- Against this computer, none. Rock beats Scissors, loses to Paper and draws with Rock, and each of those comes up one round in three. Paper and Scissors have the same split, so every move has a 1 in 3 chance to win.
- What are the odds of winning 3 times in a row?
- 1 in 27, or 3.70%: one third times one third times one third. Five wins in a row is 1 in 243 (0.412%) and ten is 1 in 59,049. Losses or draws in a row have the same odds; the page shows a streak once it reaches two.
- How is the win rate calculated?
- Wins divided by all rounds played, draws included, to one decimal place: 4 wins, 3 losses and 3 draws give 40.0%. Over a long run it settles near 33.3%, not 50%, because a third of the rounds are draws.
- How does the computer choose its move?
- When you press a button, the page asks crypto.getRandomValues for a 32-bit random number and keeps its two lowest bits, a number from 0 to 3. 0, 1 and 2 mean Rock, Paper and Scissors; a 3 (one draw in four) is thrown away and drawn again, so each move has exactly a one-third chance. Your earlier moves are not used.
- What are the rules of rock paper scissors?
- Rock beats Scissors, Scissors beats Paper and Paper beats Rock. When both sides show the same move, the round is a draw. Here a draw is not replayed: it counts as a round in the win rate.
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