Why does roulette have a 0? A roulette wheel has a 0 to increase the odds that you will lose and the house will win.
A European roulette wheel and an American roulette wheel are slightly different. They both have numbers from 1 to 36, but a European wheel only has 0, while an American one has 0 and 00. This doubles the chance that the house will win.
The difference in these odds comes in two places. It increases the odds that the house will win when players are betting on numbers, but it also increases the chances that the house will win when players are betting on red and black, which is probably the greater reason for the 0s.
Roulette is played by spinning a wheel with numbered pockets and then rolling a ball around the spinning wheel. The ball will land in a numbered pocket. It is random. The pockets are all numbered, and they are also evenly colored red or black. The 0 and the 00 are usually colored green. A player can play by betting on individual numbers, by betting on red or black, or by betting on odd or even. There are a lot of different odds, depending on the types of bets you place, but let’s just look at the odds of choosing the correct number, the correct color, or odds or evens. If you choose the correct number, the casino pays out at 35 to 1. If you put $100 on 17 and 17 comes up, you will get $3,500 back, plus your original $100. The odds of red or black or odds or evens is one to one. If you put $100 on black and 17 comes up, it is black, so you will win $100 plus your original $100 back. The same for odds and evens. 17 is an odd number, so you would win $100 plus your original $100 back.
If a roulette wheel only had the numbers 1 to 36, and a winning bet paid 35 to 1, the game would be fair. You would lose 35 times for every one time you won, on average, and the winnings would make up for the losses. You and the casino would have an equal chance of making money. However, casinos are not there just for you to have fun and win or lose money. They are there to make money. A European roulette wheel has an extra 0, making 37 possible results. An American roulette wheel usually has both 0 and 00, making 38. The payout stays at 35 to 1. This gives the casino an advantage of about 2.7% on a European wheel and 5.26% on an American wheel. That doesn’t sound like much, but over millions of bets it adds up to an enormous amount of money.
The 0 and double 0 come into play with the red/black and odd/even bets as well. If there were no 0, the odds of either one would be exactly 50:50. You would win half of the time and lose half of the time. The casino would also win half of the time and lose half of the time. That is not a good way of doing business. The 0 on a European table changes the 50:50 to 51.35:48.65. That difference between the two odds is the 2.7% advantage we saw in the European table. With the American table and the double zero, it becomes 52.63:47.37. That doesn’t sound like a lot but the small shift can add up for the casino. If you only bet once or ten times, the casino might lose and you might win. But if you bet hundreds of times, and everybody in the casino bets millions of times, it is enough for the casino to make a lot of money. We only think of the game we are playing or the games we will play that night, but a casino thinks in terms of all the games that will be played that year.
The roulette wheel was invented in France in the 18th century. The word roulette means little wheel in French. Early wheels were pretty much identical to modern wheels, although all of the wheels had both a zero and double zero. A description with a wheel in 1796 honestly said that these two spaces were to give the bank “its sole mathematical advantage”. Modern American tables have descended from those original European tables, but the European wheel changed in 1843. In the German town of Bad Homburg, two Frenchmen made a wheel with only a single zero to get more customers. They reasoned that the slightly smaller house advantage would bring in more clients, which would mean they made more money overall through the volume of trade. They were right and soon all European wheels had only one zero. And this is what I learned today.
Sources
https://en.wikipedia.org/wiki/Roulette
Photo by Pavel Danilyuk: https://www.pexels.com/photo/close-up-photo-of-casino-roulette-7594180/