Roulette Odds Explained: What Every Player Should Know Before Betting

Most gambling players, analysts, experts, and even those who do not play that often agree that most games can be separated into two distinct groups. One, usually card games, relies on experience, skills, tactics, and strategy, such as poker, blackjack, and baccarat. The other is easy, simple, straightforward games with no tactics that solely rely on luck, like slot machines. However, one game exists somewhere between these two, with both luck and strategy important for a fun experience and optimal bankroll/payment balance.  

Roulette is both one of the simplest casino games to understand and one of the easiest to misunderstand mathematically. The rules are straightforward. Players predict where a small ball will land on a spinning wheel, and the casino pays according to the type of wager. What makes roulette interesting from a mathematical perspective is that the game has precisely defined probabilities, and those probabilities determine the long term advantage of the casino. Therefore, if you want to maximize your chances on a game like Stake roulette, this is what you do.

However, understanding roulette does not require believing that a particular betting system can “beat” the wheel. In fact, the central mathematical lesson of roulette is almost the opposite, where no conventional betting progression can eliminate the house edge on a fair, normally operating wheel. The most rational approach is therefore to understand the house edge, choose the version of roulette with the most favorable rules, select bets according to your desired level of variance, and control how much money you expose to a negative expectation game.

The Roulette Wheel

The first thing a player should know about the game they choose is the wheel itself. It may seem redundant and a no brainer, but it is the first crucial step since there are three major wheel configurations that players may encounter.

A European roulette wheel has 37 pockets, the numbers 1 through 36 plus a single zero. An American roulette wheel has 38 pockets: the numbers 1 through 36, zero, and double zero. And the most recent addition, some casinos now also offer a triple zero wheel with 39 pockets, but it is quite rare.

The extra zeros are extremely important. It does not merely provide another number on the layout, but increases the casino’s mathematical advantage. On a European wheel, the probability of any individual number appearing is 1 in 37, or approximately 2.70%. On an American wheel, the probability of an individual number appearing is 1 in 38, or approximately 2.63%.

At first glance, that might make the American wheel appear better because an individual number has a slightly smaller probability of appearing. But the payout for a winning straight up bet is the same 35 to 1 on both wheels. Consequently, the American wheel gives the casino a substantially larger advantage. A triple zero wheel has 39 pockets, making the house advantage even greater.

Understanding the House Edge

The most important number in roulette is the house edge. The house edge is the casino’s theoretical percentage advantage over a very large number of bets. It does not mean that the casino wins that percentage of every individual player’s session. A player can win substantially more or lose substantially more in the short run. Instead, it describes the long term mathematical expectation.

For standard European roulette, the house edge is approximately 2.70%. For standard American roulette, it is approximately 5.26%. For triple zero roulette, it is approximately 7.69%. Those figures can be derived directly from the wheel.

Consider a European straight up bet on a single number. The player receives 35 to 1 if the number appears. There are 37 possible outcomes, but only one is favorable. The expected profit from a $1 bet can be expressed as:

(1/37 × $35) + (36/37 × -$1)

This equals approximately -$0.027 per $1 wagered. In other words, the theoretical expected loss is about 2.7 cents for every dollar wagered on a standard European roulette game.

For American roulette, the equivalent calculation uses 38 possible outcomes:

(1/38 × $35) + (37/38 × -$1)

The result is approximately -$0.0526 per dollar wagered. This is the fundamental reason the additional zero matters.

Roulette Payouts Are Technically Not Fair

A useful way to understand roulette is to compare casino payouts with mathematically fair payouts. Suppose a European wheel has 37 equally likely outcomes. A $1 wager on one number has a 1 in 37 chance of winning. A perfectly fair payout would therefore be 36 to 1 in profit, because winning $36 on the favorable outcome would compensate for the 36 losing outcomes.

The casino instead pays 35 to 1. That difference creates the house edge. On an American wheel, there are 38 possible outcomes. A mathematically fair straight up payout would be 37 to 1, but the casino again pays only 35 to 1. The additional zero and double zero therefore act as built in sources of casino advantage and need to be remembered as such.

The Odds of Common Roulette Bets

Now that you know all about the wheels, on to the next big thing, the possible bets to choose from. Roulette offers different types of wagers that cover different numbers of pockets, and they are usually picked by different types of players. The following chart covers all the basics, complete with the winning probability in both wheels and the payouts and house edges.

Mind that even money bets are some of the most popular in roulette because they seem like a 50/50 chance to win. These bets include red versus black, odd versus even, or 1-18 versus 19-36. Seemingly safe, new players prefer gambling on them and sticking to it without trying anything else.

They all cover 18 numbers each and generally pay 1 to 1. On a European wheel, however, there are 37 pockets, so the probability of winning is only 18/37, or about 48.65%, while on American it is 47.37% for 18/38. The zero is the reason an even money wager is not actually a 50/50 proposition.

The Best Possible Roulette Rules

There is an even more favorable version of roulette for certain bets. Some French and European roulette tables apply rules such as La Partage or En Prison to even money wagers. Under La Partage, when the ball lands on zero, a player who has made an even money wager loses only half of the wager rather than the entire amount. For a standard single zero wheel, this can reduce the house edge on qualifying even money bets from 2.70% to 1.35%.

This is one of the most significant rule differences a player can find. Therefore, if a player is concerned primarily with minimizing mathematical disadvantage, a single zero game with La Partage or a comparable favorable rule is particularly attractive. The exact rules should always be checked because casinos can use different variations.

Does the Martingale System Work?

The Martingale is the most famous roulette betting system. The basic idea is to bet an amount on an even money outcome, such as red. After a loss, the player doubles the next wager. The theory is that eventually a winning spin will recover all previous losses and produce a small profit. The problem is that the strategy changes bet size but does not change the probability of the wheel.

Suppose a player starts with a $10 wager and doubles after every loss. The sequence becomes $10, $20, $40, $80, $160, $320, and so forth. After a relatively small number of consecutive losses, the required wager becomes enormous. A player can encounter a table limit before the progression reaches a winning spin. Even without a table limit, the player’s bankroll may be exhausted.

More importantly, the Martingale does not eliminate the house edge. Every wager still has negative expected value. The system therefore tends to produce many small apparent successes interrupted by potentially very large losses. It changes the distribution of outcomes, but does not transform a negative expectation game into a positive expectation one.