The roulette odds calculator turns a bet’s coverage into a probability and expected result. Choose European or American roulette, then a supported bet type. The calculation assumes a fair wheel with equally likely pockets and standard payouts. Results explain the model; they do not identify the next winning pocket.
Roulette odds calculator: enter the right wheel
A European wheel supplies 37 outcomes: 1 through 36 and zero. An American wheel supplies 38 because it also has double zero. The probability of a bet winning is its number of covered pockets divided by the total pockets. A straight bet covers one pocket; a color covers 18; a dozen covers 12.
The extra pocket is not a small label change. A color bet remains 18 winning outcomes while the total grows from 37 to 38. Its win chance falls from about 48.65% to about 47.37%. This calculation includes zero losses and does not model special half-loss or held-bet rules.
Compare common bets
| Bet | European win chance | American win chance | Profit multiplier |
|---|---|---|---|
| Straight | 1/37 = 2.70% | 1/38 = 2.63% | 35 |
| Split | 2/37 = 5.41% | 2/38 = 5.26% | 17 |
| Street | 3/37 = 8.11% | 3/38 = 7.89% | 11 |
| Corner | 4/37 = 10.81% | 4/38 = 10.53% | 8 |
| Six line | 6/37 = 16.22% | 6/38 = 15.79% | 5 |
| Dozen or column | 12/37 = 32.43% | 12/38 = 31.58% | 2 |
| Color or odd/even | 18/37 = 48.65% | 18/38 = 47.37% | 1 |
Figures are rounded for display. A higher winning chance is paired with a smaller winning reward. Common bets can therefore have the same edge while feeling very different over a short run.
Calculate expected value by hand
Use one unit staked. Let p be the probability of winning and b the profit multiplier. Expected net value is p × b minus (1 minus p). For a European straight bet, that is (1/37 × 35) minus (36/37 × 1), which equals minus 1/37. The average modeled loss is about 0.02703 units per unit staked, or a 2.70% house edge.
For an American straight bet, the expression becomes (1/38 × 35) minus (37/38 × 1), or minus 2/38. That is about 5.26%. These values follow from the wheel and payout, not from any prediction about where the ball will land.
Gross expected return adds the original stake back to expected net value. European standard bets return 36/37 of turnover in expectation, about 97.30%. That does not prescribe an actual session balance.
Understand the boundaries
The American five-number basket covers 0, 00, 1, 2, and 3 and commonly pays 6:1 profit. Its edge is 3/38, about 7.89%, rather than the usual 5.26%. Treat it separately if comparing physical-table bets. The calculator only computes choices offered in its interface.
Multiple overlapping bets require weighting their individual stakes. Adding win probabilities without checking overlaps can count a pocket twice. The chance of at least one win across several independent spins is another question and does not describe the chance of finishing ahead.
Use the simulator to follow a sample settlement, then return here to inspect the theoretical probability. A streak changes a sample history, not the next-spin probability in this model. The calculator does not handle wheel bias, dynamic payouts, triple-zero wheels, or regional exceptions unless explicitly offered.
Common questions
Does the tool predict a winning number?
No. It calculates probabilities and expectations under a fair-wheel assumption.
Why are color odds below one half?
The zero pockets lose on color bets and are included in the total outcomes.
Are all American bets identical in house edge?
No. The common five-number basket has a different payout-to-coverage relationship.