How Roulette Really Works

Roulette is one of my favorite games in the casino. It gets a bad rap from some gambling writers because the house edge for American roulette is relatively high (5.26%). Those writers don’t take into account other factors that affect how much you lose on average.

The purpose of this post is to get you educated about the game and how the math really works so you can make educated decisions about whether you want to play. And if you do want to play, this post offers some guidance on how to do so without being too disappointed when you walk away a loser.

Plenty of people would love to sell you some kind of betting system for roulette. This post explains why you should keep that money. I’ve also included some insights into the pros and cons of such decisions.

Here’s the truth about how roulette really works:

Playing Roulette Is Mind-Numbingly Simple

Roulette is one of those “spinning wheel of fortune” type of gambling games. The wheel is in a large bowl of sorts on the table, and it has 38 possible outcomes (pockets).

The pockets are colored and numbered in the following way:

There’s a green 0 and a green 00, for a total of 2 green pockets.
There are 18 black numbers.
There are 18 red numbers.
There are 38 numbers total.
The black and red numbers are numbered 1 through 38.

You bet in roulette by placing chips on the betting surface on the option you think might come up next.

You can place 1 of 2 kinds of bets:

Inside bets
Outside bets

Which bets you place should be based on your risk tolerance and what kind of gambling you enjoy. All of the bets (except one) have the same house edge, but some of the bets have big payouts based on longer odds.

The most basic outside bet in roulette is the even-money bet. You can bet on whether the ball will land on black or red, odd or even, or high or low.

If the ball lands in the right spot, this bet pays off even money—you bet $100, you win $100.

Some people are confused about the actual probability of winning these even-money bets, though. They look like they’re a 50/50 shot, and if it weren’t for those 2 green 0 pockets, they would be.

You can also bet on individual numbers. This bet pays off at 35 to 1 if your number hits, but the odds of hitting a single number are 37 to 1. It probably isn’t hard to see where the house gets its edge based on this, but I’m still going to discuss that in detail in the next section.

You can also bet on 2 numbers, 3 numbers, 4 numbers, or 5 numbers. You can bet one 12 numbers at a time, too. The payoffs are go down the more numbers you cover with each bet.

In the long run, it doesn’t matter if you place single-number bets all night or even-money bets all night. The house edge is the same, 5.26%.

The Truth about How the House Edge Works in Roulette

If you’ve read any of the other posts in this series, you already know what the house edge is and how it works. It’s a long-term prediction of how much you can expect to lose per bet when you play a casino game. It’s expressed as a percentage.

It’s easy to understand if you think about what would happen if you ran through 38 perfect spins betting $100 each. Say you placed a single-number bet. You’d win once, and you’d win $3500.

But you’d lose 37 times, losing $100 each time, or $3700. That’s a net loss of $200 over 38 spins, or $5.26 per spin. That’s 5.26% of what you bet each time.

All the bets in roulette have the same 5.26% house edge but one—the 5-number bet. This is a bet that 0, 00, 1, 2, or 3 will show up. It’s also called the “basket bet.” It pays off at 6 to 1 odds.

But the probability of winning this bet is a little rougher. Using the same procedure as before, you can see that you would lose 33 times for $100 each, for a loss of $3300. You’d win 5 times at $600 per win, for winnings of $3000. Instead of a net loss of $200, you have a net loss of $300. That’s $7.89 on average per spin, or 7.89%.

In the short run, of course, you’ll see what mathematicians call “variance.” You’ll win more often or lose more often than the mathematical expectation predicts. That’s one of the reasons people still play the game.

But there’s no real way to take advantage of that variance to your advantage. In the long run, a negative expectation game is a negative expectation is a negative expectation game.

Also, 5.26% isn’t as bad as you think. A better measure for a casino game’s probability is probably your average loss per hour.

Roulette is a slow-paced game. If you’re disciplined, you can limit the number of bets you make per hour. I’d suggest only placing a single bet on each spin—although plenty of players make multiple bets per spin.

The more money you put on the table, though, the more money you stand to lose. The amount of money you’re expected to lose in an hour on the roulette table is the average amount of your wagers multiplied by the wagers per hour multiplied by the house edge.

Most roulette games move pretty slowly. We’ll call the average 50 spins per hour, but it might be considerably lower than that at a busy table. (When the croupier is paying off bets and selling chips, he’s not spinning the wheel.) If you’re betting $5 per spin, that’s $250 per hour in action. 5.26% of that action is $13.15 per hour.

Can You Do Anything to Decrease the House’s Mathematical Edge in Roulette?

The truth is, there’s nothing you can do to decrease the house’s edge in roulette besides choosing the better tables. Oh, yeah? Didn’t I mention that?

All the rules and numbers I’ve mentioned so far are for a standard American roulette wheel with standard rules in the United States. Different versions of roulette exist, and you should play some of them if you can.

The first thing you should do if you like roulette is try to find a “single-zero roulette” wheel. This is also sometimes called a “French roulette game” or “European roulette game.” This variation only has a total of 37 pockets. It eliminates the green 00 pocket. This changes the house edge from 5.26% to 2.70%. Instead of losing $13.15 per hour, you’re now losing $6.75 per hour.

And I don’t know of any reason to think that an American roulette game is somehow more fun than a European roulette wheel. Everything is the same besides the elimination of the awful 5-number bet and a big chunk of the house’s edge.

You can also find casinos which offer an optional rule called the “en prison” rule. This is a rule that when you lose an even-money bet, your bet isn’t taken by the house. Instead, it’s put “in prison” until the next spin.

On the next spin, if your bet loses again, it’s lost forever. But if it wins this time, you get your original bet returned to you (with no winnings, of course.) This cuts the house edge in half on the even money bets, to 1.35%.

Now you’re looking at a game that’s comparable to craps or blackjack, and you don’t need to know any kind of strategy or have any kind of skill to take advantage of this low hourly rate for entertainment.

Also, you’re more likely to walk away from the table a winner the lower the house edge is.

The Truth about Getting an Advantage at Roulette

The truth is that you can’t get an advantage at roulette. It’s not like blackjack, where you can learn how to count cards. Even dice control in craps is more likely to net you an edge than any technique you might try at the roulette table.

The only remotely legitimate technique for getting an edge at roulette is to look for a wheel that’s “biased.”

In a perfect world at a perfect casino, a roulette wheel would work perfectly. But in real life, some wheels wind up a little warped. On these wheels, it’s possible to spot a bias toward certain numbers. If the bias is strong enough, you could theoretically get an edge by betting on these numbers more often.

The problem is that such a bias is most likely small. It’s certainly not going to be visible to the naked eye or the casual observer.

The only way to spot a wheel with such an imperfection is to clock the results for hundreds, maybe even a thousand spins. Good luck with that.

Can you imagine how boring it would be to track a roulette table’s results for 12 or 18 hours straight?Even then, you’d occasionally need to take breaks to sleep. That means you’d probably need at least one teammate.

Also, most casinos frown on this kind of advantage play technique. They’re not going to just let you sit there and clock their wheel. You’ll have to find a way to do this subtly. I’m not sure what the trick would be to pull that off, but I’m sure there is one.

Imagine this, though—you put in all that work, and it turns out that the roulette wheel shows no evidence of any bias at all. Worse, what if it shows a bias, but that bias isn’t really there? It could just be a statistical aberration.

The law of large numbers suggests that with enough repetitions, you’ll get close to the mathematical expectation. This doesn’t mean that you’ll always get to the mathematical expectation, though.

In any series of random results, you could face a false positive. Maybe if you tracked the same wheel for a month or 2, you could be really confident that you’ve found an actual bias. But who wants to do that?

What about Betting Systems Like The Martingale System?

Some roulette players think systems like The Martingale System are fool-proof. At first glance, they seem to be. In fact, The Martingale System is one of the easiest betting systems in the casino.

To use this system, all you have to remember is that you double the size of your previous bet if your previous bet lost. When you win, you return to your initial bet size.

In this way, you’ll always recoup your losses plus a win the size of your initial bet. Oh, yeah—this is a system you’ll want to use on the even-money bets, like black or red.

Here’s an example of The Martingale System in action:

You bet $5 on black and lose. You bet $10 on black again on the next spin, and you lose again. So on your 3rd bet, you place a $20 wager.

You lose again—this makes 3 times in a row! Now you must place a $40 wager. Finally, you win, but you’re only up $5, because you lost on the 3 previous spins.

This does indeed sound fool-proof, but it doesn’t take into account the exponential increase in the size of your bets over a relatively short period of time.

If you lose 8 times in a row, the next bet is huge–$1280. At most casinos, that size bet will put you over the table limits. The casinos have both minimum and maximum bet sizes to consider. At a table with a $5 minimum, you’ll sometimes see a maximum betting limit of $1000, but just as often, you’ll see a maximum betting limit of $500.

Most people underestimate how often a losing streak of 8 or 9 spins happens. It’s rare, sure, but it probably happens at least once a day at most roulette tables. In actual practice, you’ll see lots of small winning sessions playing roulette with The Martingale System.

But you’ll inevitably run into a big losing session, and that losing session will wipe out your winnings from the previous sessions. The house edge in roulette is a lot like Joe Lefors in the movie Butch Cassidy and the Sundance Kid. It’s relentless and impossible to escape from in the long run.

Other gambling systems exist though, like The Paroli System, which I’ve also seen called “The Anti-Martingale” or “Reverse Martingale.” Instead of doubling the size of your bets every time you lose, you double the size of your bets every time you win. Your goal with this system is to capitalize on a winning streak. You’ll have occasional huge winning sessions, but 80% of the time, you’ll have small losing sessions—which is exactly the opposite of what you would expect from The Martingale System.

What these systems have in common is the implicit belief in something called The Gambler’s Fallacy. This is the belief that previous results somehow affect future results.

You’ll meet 2 kinds of uneducated gamblers in the casino. One will think that if red has come up 8 times in a row at the roulette table, the probability of getting black on the next spin has increased.

The other will think that if red has come up 8 times in a row at the roulette table, it’s more likely that you’ll get red again on the next spin, because red is “hot.”

Neither of these gamblers is right. The probability of getting red or black remains the same, because each spin is an “independent event.” On a standard American roulette wheel, you have a 47.37% probability of getting red, and a 47.37% probability of getting black.

The previous results don’t affect the probability on the next spin. System believers will ask you how probable it is to get red 9 times in a row, though?

They’re right. That is unlikely. But you’re not betting on getting red 9 times in a row. You’re betting on the outcome of the next spin.

And we’ve already established the probability of winning an even-money bet on a single spin of the roulette wheel. It’s 47.37%.

Conclusion

Roulette’s a great game, because it requires no skill at all to play. Even though the house edge is a little higher than most people would prefer, if you can find a roulette game with a single zero and the en prison rule in place, you can be playing one of the best games in the casino—a game that’s comparable to blackjack or craps in fact.

But even if the best game you can find is a standard roulette game with an American wheel, you still won’t lose much per hour. That’s because the rate of play is relatively slow—especially when compared to how many bets per hour you’ll make playing slots.

Roulette gets a bad rap. But it doesn’t deserve it. And that’s the truth about how roulette really works.