Roulette – The Impact of the Zero

Adding a zero or two is a subtle move by the house to shift the odds in its favour, but is not present in all variants of the game. If you look at the betting layout, you’ll notice that as well as being able to bet on individual numbers there are certain group bets that you can make, such as odd or even; red or black, but the zero is not included in these.

Let’s take red vs. black as an example. Without the zero, the odds of winning a bet placed on one of these should be 50%. Including the zero on the board (usually coloured in green, so excluded from both of these), the odds of a bet placed on either red or black is slightly reduced. We’ll show you this mathematically in the next paragraph, so feel free to the next heading if you want…

On most boards, there are 36 numbered slots split evenly between red and black, so the chance of the ball landing in either a red or black slot would be 18 out of 36 = 50%. Adding the zero, means that it’s now 18/37, which is only 48.6% chance of you winning now. Whilst this doesn’t sound like much, casinos play the long game – looking at average results over time rather than the results of individual sessions.

This is where the statistics kick in – this basically says that if you go for a long enough period of time, the effect of unusual outcomes (like a player having a massive win, or a massive loss) is smoothed out, and the result of the game will be in line with the calculated percentage chances of winning. This means that the tiny percentage that the zero brings to the game is a massive deal for the casino, but doesn’t really have a big impact on your experience for a single playing session.

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