Roulette rules and house edge

Roulette is a wheel game. A ball lands in a numbered pocket, and bets paid at fixed odds win or lose according to that number and its color or other properties. The house edge comes from the zero pockets, which are losing outcomes for the usual even-money and many inside bets.

A standard European (or French) wheel has 37 pockets: 1 through 36, plus a single 0. For a typical even-money bet, such as red or black, 18 pockets win and 19 lose. The probability of winning is 18/37. A fair even-money game would pay as if the chance were one-half. The difference is the house edge: 1/37, which is about 2.70 percent. The same 1/37 edge applies to the standard straight-up and many other inside and outside bets on a single-zero wheel (a special French rule called “en prison” or “le partage” can reduce the edge on even-money bets only; do not assume that rule applies online unless it is stated).

A standard American wheel has 38 pockets: 1 through 36, plus 0 and 00. For the same even-money bet, 18 pockets still win, but 20 lose. The house edge is 2/38, which is about 5.26 percent. That figure is almost twice the European edge and is the reason an American wheel is a worse long-run game, all else equal.

A “0 and 00” wheel is not made fair by betting both colors or both even and odd in some combination. Those bets still lose when the ball lands on a zero. Systems that double after a loss, sometimes called martingales, do not remove the edge. They only change the pattern of wins and losses and can produce a very large single loss when a table limit is reached. On a standard single-zero or double-zero layout, the usual inside bets (straight-up, split, street, corner, line) and the usual outside bets (red or black, even or odd, columns, dozens, and the low or high half) all carry the same house edge as the wheel itself: 2.70 percent on a 37-pocket wheel and 5.26 percent on a 38-pocket wheel. That is because the payouts are set as if the zeros were not there. The American five-number bet is a well-known exception with a worse edge. French-style tables sometimes use the same single-zero wheel as European roulette but add a shared-loss rule on even-money bets when the ball lands on zero. If a licensed game clearly posts la partage or en prison, the long-run edge on those even-money bets is lower than 2.70 percent. If the rule is not posted, assume it does not apply. Wheel speed, a dealer’s hand, or a previous run of colors does not change the next spin.

Some casinos offer a “five-number” bet on American wheels covering 0, 00, 1, 2, and 3. That bet has a higher house edge than the usual 5.26 percent and is one of the worst standard roulette wagers. If a layout highlights it, that is marketing, not generosity.

Online, confirm whether the game is single-zero or double-zero before you play, and only use a licensed U.S. site in a state that has authorized internet gaming. See the state legality guide.

See also: all game guides, where online casinos are legal, and responsible gambling help.