In order to calculate the house edge, we will apply the following formula: (Odds Against Winning – House Odds) * Probability of Winning * 100 = house edge percentage. Like we mentioned above there is an 18 in 37 chance for us to win this bet, meaning that in 19 out of 37 we would lose. The payout for winning a bet on red is 1:1 but this is not reflected in the odds. That means there is a 1/37 (=0.027) chance of landing on green, in which case the casino keeps the bets.

Placing an outside bet (e.g on red) gives you an 18/37 chance of winning, similarly for black. Firstly, we consider a European roulette table, so that there are thirty-six numbers which are red and black, and a green zero.