The difference between odds and payouts
In roulette, probability is the chance that a bet wins; the payout is what the table credits when it hits, usually stated as profit relative to the stake. A payout of 35 to 1, for example, means 35 units of profit for every unit wagered, with the original unit returned as well.
These measures are not the same. A bet can win more often and pay less, or be harder to hit and pay more. To understand roulette probabilities and payouts, first check how many pockets are on the wheel: European roulette has 37, numbered 0 through 36; American roulette has 38 because it includes both 0 and 00. The layout changes the odds and the house edge.
Probabilities and payouts for common bets
On a European wheel, each number has a probability of 1 in 37, or about 2.70%. A straight-up bet on one number pays 35 to 1. A bet covering two adjacent numbers has a 2-in-37 chance (about 5.41%) and pays 17 to 1. Bets covering three, four, six, or twelve numbers cover more outcomes but pay less when they win: 11 to 1, 8 to 1, 5 to 1, and 2 to 1, respectively.
Outside bets such as red/black, odd/even, or high/low cover 18 numbers on a European wheel. Their chance of winning is 18 in 37, approximately 48.65%, and the usual payout is 1 to 1. Zero is not red or black, odd or even, or high or low, so these bets do not have a 50% chance on a wheel with a zero. On an American wheel, 00 can also make the bet lose: for an outside bet, the chance falls to 18 in 38, approximately 47.37%.
How to check expected return
Consider a $1 straight-up bet on a European wheel. If it wins, the profit is $35; if it loses, the loss is $1. Expected value is (1/37 × $35) − (36/37 × $1), or about −$0.027 per spin. That corresponds to a house edge of approximately 2.70% for this wheel. It does not mean every player loses that amount on every spin: it is a long-run mathematical average, not a prediction of an individual result.
Outside bets on the same wheel have the same theoretical proportional loss when they pay 1 to 1: (18/37 × $1) − (19/37 × $1), also about −$0.027 per dollar wagered. On an American wheel, the house edge is higher under standard payouts because there is an additional pocket without a proportional increase in the prize. Special rules can change the calculation, so check the table’s payout and rules before betting.
A catalogue example and a practical caution
Bettbit’s public catalogue includes Roulette. Check the table’s own information screen to see whether it has 0 or 00 and to confirm the applicable payouts.
To compare bets, calculate the chance by dividing the pockets covered by the total number on the wheel, and read the payout as profit rather than probability. Do not raise your stake to chase losses: previous outcomes do not change the next spin, and the mathematical edge does not disappear during a short run.