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Roulette Probability Calculator

See the real odds, payouts and house edge for common bets.

This calculator lets you choose a roulette wheel type and bet type, then instantly see the true probability of winning, the fair payout, the actual casino payout, and the house edge. It is designed as a learning tool so you can connect every roulette bet back to real numbers, not guesses or myths.

Select whether you are dealing with a European (single-zero) or American (double-zero) wheel, choose your bet, and optionally adjust your stake size to see the expected value of a single spin.

🎯 European & American wheels 📊 Win probability & house edge 💰 Expected value per spin

Calculate roulette odds for your bet

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Used to show expected value in money terms. Does not change percentages.

How this calculator works

For each bet type, the calculator counts how many numbers on the wheel give you a win, divides by the total number of pockets, and converts that into probabilities and expected value. The house edge is simply the percentage of each bet the casino keeps on average over the long run.

Formulas in plain language

  • Win probability
    Numbers covered ÷ total pockets. For example, an even-money bet on a European wheel covers 18 of 37 numbers.
  • Fair payout
    If there were no house edge, a fair payout would be (1 / win probability) − 1. The calculator shows this as “fair odds to 1”.
  • Expected value
    For a $1 stake: EV = (win prob × payout) − (lose prob × 1), where “payout” is the net win (for example, 35 for a 35:1 payout).
  • House edge
    The house edge is −EV expressed as a percentage. If EV is −$0.027 per $1 bet, the house edge is 2.7%.

Use this as a teaching tool, not a betting system

This calculator is here to make the math of roulette visible. It does not turn negative expectation bets into investments, and it does not remove risk. Whatever system you use on top of these bets, the underlying probabilities and house edge stay the same.

For deeper context, explore the systems library and the learn roulette section, and always review the responsible gambling guidelines before risking real money.