The European Roulette wheel has thirty-seven spaces, which are all numbered and colored. The numbers range from one to thirty-six, and contain a single zero. The single zero is colored green, while half the numbers on the European Roulette wheel are colored red and the other half have black coloring. The reason the zero is green on the European Roulette wheel is that this number is a neutral number. It is neither even nor odd, and pays neither red bets nor black bets. The expected return on most European roulette bets in their pure form is a negative $.027 per dollar bet on each spin.

Different variations in European roulette change the house edge. A mere adjustment to the rules can shift the odds towards or further away from the player. One variation of European roulette allows players to have a chance to win their bet back when the ball lands on zero. This is known as imprisonment (en prison). The imprisonment rule only applies to bets that pay evenly, such as the red/black, odd/even, or high-low outside bets. Under the imprisonment rules, this variation of roulette calls for such bets to be locked down on the spin following the occurrence of zero. If the player wins their bet on the next spin, they are awarded a refund of their bet. While they are provided a rebate on their imprisoned bet, they are not entitled to the winnings associated with the bet. European roulette games that employ this specific variation on the rules of roulette enjoy an edge of approximately 1.3%.

Other online casinos that offer European roulette provide a variation of the imprisonment rule. The most common roulette variation of imprisonment is called “La Partage,” which translates to the division. Like the translation suggests, when a player has an even money bet and the ball lands on zero, the even money bets are divided. Half the bet goes to the house, while half is returned to the player. This variation of the imprisonment rule provides the house with a 1.35% edge. Other casinos allow imprisoned bets to move to other even money bets. In this European roulette variation, the house maintains an edge over the players of nearly 1.39%.

When compared to its American roulette counterpart, the expected loss per bet is less in European roulette. American roulette players can expect to lose around $.05 per bet on average. When given a choice between variations of roulette, European roulette (preferably with imprisonment privileges) is clearly the way to go.