The number that changes every bet on the table
A player walking up to a roulette table usually looks at the felt first. The smarter first look is at the wheel itself, because one small difference in the wheel changes the odds on every single bet available. A European roulette wheel has 37 pockets: the numbers 1 through 36 plus a single zero. An American wheel has 38: the same 36 numbers plus both a single zero and a double zero. That one extra pocket is not decoration. It is the single largest factor in how fast a bankroll drains on otherwise identical bets.
The numbered pockets alternate red and black around the wheel. The zero pockets are green. The sequence of numbers around the wheel is deliberately arranged so that high and low, odd and even, and red and black are scattered rather than clustered, but the sequence does not affect the mathematics. What matters is the count: 37 or 38 equally likely outcomes, and the payout on a winning bet is calculated as if the zeros did not exist.
Reading the two wheel layouts
Roulette is the same game on either wheel. The dealer spins the wheel in one direction and sends the ball travelling the other way around a sloped track. The ball loses momentum, drops onto the wheel, bounces across the frets between pockets, and settles. If the pocket it settles in matches the bet, the bet wins. The difference between the two wheels is entirely in which pockets exist and what that does to the payout structure.
| Feature | European wheel | American wheel |
|---|---|---|
| Total pockets | 37 | 38 |
| Numbered pockets | 1 to 36 | 1 to 36 |
| Zero pockets | One (single zero) | Two (single and double zero) |
| Colour of zero pockets | Green | Green |
| House edge on a straight-up bet | Lower | Higher |
| Common rule variants | En prison or la partage on some tables | Rarely offered |
The house edge on any roulette bet is the gap between the true odds of the event and the payout the table offers. On a European wheel, a straight-up bet on one number pays 35 to 1. There are 37 pockets, so the true odds against hitting that number are 36 to 1. The missing unit is the house edge. On an American wheel the same 35 to 1 payout is offered against 37 to 1 true odds, because the double zero adds one more losing pocket. That is why the American layout carries a larger edge on every bet, not just the zero bets.
What a round looks like
The sequence from standing at the rail to collecting a win is the same on both wheels. First the player buys in: cash or a casino cheque is placed on the felt, never handed directly to the dealer, and the dealer exchanges it for wheel-specific colour chips. These chips have no denomination printed on them. The dealer assigns each player a colour so that bets on the layout can be identified at a glance, and the value of that colour is set when the player buys in. Colour chips must be exchanged back at the table before leaving; they are not valid at the cashier cage.
Once players have chips, the dealer opens betting. Players place chips on the layout in the positions that correspond to their chosen bets. The dealer announces that no more bets may be placed, spins the wheel, and releases the ball. When the ball settles, the dealer places a marker on the winning number, clears all losing bets from the layout first, and then pays winning bets. Players may not touch their chips after the no-more-bets call, and they may not place or remove bets while the ball is in motion.
The bet types and why the edge differs between them
Every roulette bet is a wager on where the ball will land. The bets differ in how many pockets they cover and how much they pay. Covering more pockets means a higher chance of winning each spin but a smaller payout; covering fewer pockets means a lower chance but a larger payout. The house edge on most bets is the same within a given wheel type, but there is one important exception on the American layout.
| Bet | Pockets covered | Payout | What it means |
|---|---|---|---|
| Straight-up | 1 | 35 to 1 | A single number |
| Split | 2 | 17 to 1 | Chip placed on the line between two numbers |
| Street | 3 | 11 to 1 | A row of three numbers |
| Corner | 4 | 8 to 1 | Four numbers meeting at one corner |
| Six line | 6 | 5 to 1 | Two adjacent rows |
| Red or black | 18 | 1 to 1 | Colour of the winning pocket |
| Odd or even | 18 | 1 to 1 | Parity of the winning number |
| High or low | 18 | 1 to 1 | 1-18 or 19-36 |
| Dozens | 12 | 2 to 1 | First, second or third block of twelve |
| Columns | 12 | 2 to 1 | A vertical column on the layout |
On a European wheel, every bet in that table carries the same house edge. On an American wheel, one bet is worse than the rest: the five-number bet covering 0, 00, 1, 2 and 3. It pays 6 to 1, but the true odds against it are 33 to 5, which leaves a larger gap than any other American roulette wager. The lesson is not that other bets are good and this one is bad. It is that the edge is not uniform across the whole table, and a player who wants to know what they are paying should check the wheel type and the specific bet before the chips go down.
Where the zero goes and why it matters
The zero pockets are what create the house edge on the even-money bets. A bet on red covers 18 pockets on either wheel. On a European wheel there are 19 pockets that are not red: the 18 black numbers plus the single zero. On an American wheel there are 20: the 18 black numbers plus both zeros. The payout on red is still 1 to 1. The zero is not a push on most roulette tables; it is a losing pocket for red, black, odd, even, high and low. That is the entire mechanism by which the operator keeps an edge on bets that feel like coin flips.
Some European tables offer a rule called en prison or la partage on even-money bets. When the ball lands in zero, the player either gets half the bet back or the bet is held in prison for the next spin, depending on the rule. This reduces the house edge on those even-money bets specifically. It does not change the edge on inside bets, and it is far more common on European layouts than American ones. A player who sees the rule posted should understand it applies only to the bets the rule names.
Mistakes that cost more than the wheel type
The most common procedural mistake is touching chips after the dealer has called no more bets. Roulette is a game of simultaneous betting, and the layout is crowded. A hand in the wrong place after the call can be read as an attempt to alter a bet, even when the player is only pointing. The second is treating colour chips as cash. They are table-specific and must be converted before walking away. The third is assuming the wheel type from the table minimum or the room's decor. The wheel itself is the only reliable indicator: count the zero pockets before the first bet.
There is also a persistent belief that previous spins tell a player something about the next one. Each spin is an independent event. A wheel is a physical object and can have mechanical biases, but modern wheels are maintained and tested to keep outcomes effectively random, and no betting system based on past numbers changes the built-in edge. The wheel does not remember, and neither does the ball.
FAQ
Is there a roulette wheel with more than 38 spaces?
Some novelty or promotional wheels add extra pockets, but the two standard layouts are the 37-pocket European wheel and the 38-pocket American wheel. Any additional pocket changes the odds on every bet, so a player should read the posted rules before playing an unfamiliar layout.
Why does the American wheel have two zeros?
The double zero was added to the layout as the game spread through American gambling houses in the 19th century. It gives the operator a larger edge on every bet because it adds one more losing pocket without changing any payout.
Do the zero pockets pay more than other numbers?
A straight-up bet on zero pays the same 35 to 1 as a straight-up bet on any other single number. The zero pockets are not higher-paying; they simply exist as pockets that lose for the even-money and most other outside bets.
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This article is general information about how these mechanics work. It is not legal advice and not a recommendation to gamble or to use any particular operator. Availability and legality differ by jurisdiction — check the rules that apply where you are.