How many numbers are on a roulette wheel, and why it matters

Both wheels pay the same: 35:1 on a single number, 2:1 on a dozen, even money on red. The payouts are set as though there were 36 numbers. A 37th pocket means the house keeps 1/37 of all money bet on average, which is 2.70%. A 38th pocket makes it 2/38, or 5.26%. Nothing else about the two wheels differs in a way that affects your money.

So when a lobby offers both, the European wheel is the one to sit at, every time, for every bet.

Eighteen red, eighteen black, one or two green. The reds on a standard wheel are 1, 3, 5, 7, 9, 12, 14, 16, 18, 19, 21, 23, 25, 27, 30, 32, 34 and 36. The blacks are the rest of 1 to 36. On the betting layout the colours alternate in a way that looks random but is fixed; on the wheel itself they strictly alternate red, black, red, black around the rim, with the green pocket or pockets breaking the pattern.

The numbers are not in sequence around the wheel. The European order, clockwise from zero, is: 0, 32, 15, 19, 4, 21, 2, 25, 17, 34, 6, 27, 13, 36, 11, 30, 8, 23, 10, 5, 24, 16, 33, 1, 20, 14, 31, 9, 22, 18, 29, 7, 28, 12, 35, 3, 26. It is arranged so that reds and blacks alternate, high and low numbers are spread fairly evenly, and odd and even are mixed. The American wheel uses a different order with the 0 and 00 opposite each other.

The order matters for one family of bets: neighbours and the French section bets, which cover arcs of the wheel rather than rows of the layout. The wheel-layout page has the full sequence with the sections marked.

Among 1 to 36 there are eighteen odd and eighteen even numbers, and eighteen low (1 to 18) and eighteen high (19 to 36). Zero is none of these. That is why every even-money bet, red, black, odd, even, high, low, covers exactly 18 pockets and loses on the green.

Without it, a bet on red would win exactly half the time and pay even money, and the casino would make nothing. The zero is the house's share. Early wheels had both a zero and a double zero; the single-zero wheel was introduced in the 1840s to attract players with better odds, and it worked. The double-zero wheel survived in America, which is why it carries that name.

RNG roulette games simulate a 37- or 38-pocket wheel and the result is drawn uniformly from those pockets. Live tables use a physical wheel on camera. Either way the count is the same and the maths is the same. The one thing to check on any new table is the number of green pockets, because it is the one number on the whole layout that changes what you pay.

Which number is coming. Each of the 37 is equally likely on every spin, whatever happened before. A wheel with 37 numbers is a wheel where your number comes up about once in 37 spins, on average, with long gaps and short clusters along the way. RouletteFinder has a fuller guide to the wheel and the layout together, including how the table bets map onto the physical wheel.