(This means that for every 37 spins, you can expect to win once on average.) In European roulette, the probability of winning a straight bet on a single number is 1/37 or approximately 2.70%.It is usually expressed as a percentage or a fraction. On the other hand, it refers to the likelihood of a specific event occurring in the game.(This means that if you win, you’ll receive 35 times your original bet in addition to getting back your initial wager.) If you bet on a single number (straight bet) in American roulette, the odds are 35 to 1.They are usually expressed in the form of a ratio or fraction. This represents the payout a player can expect to receive for a winning bet.While both terms relate to the likelihood of winning, they hold distinct meanings that profoundly impact players’ understanding of the game and their betting strategies. Roulette odds and probability are two essential concepts that dictate the outcome of each spin. Understanding Roulette Odds and Probability The objective of playing roulette is to predict and bet on the winning number or group of numbers that the ball will land on after the wheel is spun.