What are the true odds against winning ‘outside’ bets in roulette?
Confusingly, ‘outside’ bets in roulette are so-called not because they offer an outside chance of winning – they offer odds of 1/1 or 2/1 so, in fact, the exact opposite – but simply because of their position on the roulette table. The bets available are red/black, odd/even and first 18/second 18, all at 1/1, and first/second/third column and first/second/third dozen, both at 2/1.
Of course, the presence of a green single zero, on a European roulette wheel, and an extra green double zero – and, in some cases, an additional green triple zero – on an American roulette wheel, is what creates the ‘house edge’ and reduces the probability of winning outside bets. On a European roulette wheel, an even money bet on, say, red or black, does not have a 50% chance of winning, but rather a 48.64% chance, while bets on any column or dozen have a 32.4%.
On an American roulette wheel, an extra green double zero pocket also puts paid to all outside bets and increases the house edge to 5.26% from 2.70% when compared to single-zero roulette. In the double-zero version, the probability of a winning 1/1 bet is further reduced to 47.38%, while the probability of a winning a 2/1 bet becomes 31.58%. Triple-zero roulette, which is becoming increasing popular in Las Vegas and elsewhere, does the player fewer favours still, other than offering a lower table minimum stake than the double-zero version. For this ‘privilege’, the player pays an extra 2.5%, in terms of house edge, while the probability of winning outside bets is further reduced, to 46.15% and 30.77%, respectively.