Roulette is a recognizable casino game built around a spinning wheel and a small ball. Its rules are relatively straightforward but the mathematical principles behind the game provide an interesting example of probability and expected value. Understanding these principles helps explain why different betting options have different chances of success.

A roulette wheel contains numbered pockets arranged around its circumference. European roulette includes numbers from zero through thirty six giving it thirty seven pockets. American roulette usually includes an additional double zero which brings the total to thirty eight pockets. This difference affects the probability of winning on many standard bets.

In European roulette a bet on one specific number has a probability of one in thirty seven of winning. In American roulette the probability is one in thirty eight. Although the difference may appear small it changes the mathematical advantage held by the casino.

Roulette offers several betting categories. Inside bets involve individual numbers or small groups of numbers. Outside bets cover broader categories such as red or black odd or even and high or low numbers. Broader bets man club generally have a greater chance of winning than a single number bet but their payouts are correspondingly smaller.

The house edge represents the casino's theoretical advantage under the game's standard rules. In common European roulette the house edge is approximately 2.70 percent. In standard American roulette it is approximately 5.26 percent. These percentages describe long term mathematical expectations rather than the result of any individual session.