Roulette is one of the oldest casino games still played largely unchanged: a spinning wheel, a small ball, and a betting layout where players guess where the ball will land. Its rules are simple, but understanding the wheel itself explains almost everything about the game's odds.
Two wheels, two edges
There are two main versions of the wheel. European roulette has 37 pockets, numbered 0 to 36. American roulette adds a second zero, giving 38 pockets in total. That single extra pocket changes the maths considerably: European roulette carries a house edge of about 2.7%, while American roulette's edge is roughly 5.26%, almost double, because the extra 00 pocket does not pay out to any outside bet. In both versions, the ball's landing spot is determined entirely by physics, the spin of the wheel and the bounce of the ball, with no way for a player to influence or predict it.
How the bets pay
Bets fall into two broad groups. Inside bets cover specific numbers or small groups of numbers and pay out at higher odds because they are less likely to win; a single straight-up number bet, for instance, pays 35 to 1. Outside bets cover larger groups, such as red or black, odd or even, or high or low, and typically pay even money, meaning a 1:1 return on a win. Players can also mix bets across both categories in the same spin, spreading coverage across the layout.
- Straight up – a single number, highest payout
- Split – two adjacent numbers
- Street or corner – three or four numbers
- Red/black, odd/even, high/low – even-money outside bets
Why the edge never disappears
Because the zero (and, in American roulette, the double zero) does not belong to any colour or odd/even grouping, every outside bet is very slightly against the player over the long run, no matter how the numbers have landed recently. Past spins do not influence future ones; the wheel has no memory, and a run of reds makes black no more or less likely on the next spin, a common misconception known as the gambler's fallacy. Roulette is best approached as a game of chance for entertainment, with spending limits decided in advance and kept to, rather than as a system that can be studied or predicted over time.
