How to Use the RPS Win Probability Calculator
Choose your effective win rate per round (50% if ties are replayed, 33.3% if ties count as a loss), enter the number of rounds and your target win count, then pick a calculation mode. The tool uses the binomial distribution formula to give you an exact probability.
Use "At least K wins" for best-of-N series, "Exactly K wins" for fixed-result puzzles, and "K consecutive wins" to find out how rare a win streak really is.
Frequently Asked Questions
If players replay ties until someone wins, each decisive round is 50/50 — use 1/2. If ties end the match in favor of the opponent, use 1/3.
Yes — any game with a fixed per-round win probability and independent rounds works the same way. Just note that this tool defaults to 1/2 or 1/3 for RPS.
It is the average number of wins you would get if you played the same N rounds many times: N × win rate. It does not guarantee that outcome in any single match.