Roulette, like all gambling games, is all about odds. To get the most out of your roulette play it is critical to know how often you can expect to win and how much of an advantage you need to overcome.
At the most basic level, we talk about roulette odds in terms of the house edge – the advantage the casino holds over the player. In American roulette the house edge on virtually all bets is 5.26% (or 2/38), while in European roulette, the edge for the casino is 2.70% (1/37). Essentially, you can figure out the edge by dividing the number of zeroes on the wheel by the total number of pockets. That is true at least for standard roulette games that pay out at odds that would be fair if the wheel only contained the 36 numbers without zeroes.