Casino games generally provide a predictable long-term advantage to the casino, or “house”, while offering the player the possibility of a large short-term payout. Some casino games have a skill element, where the player makes decisions; such games are called “random with a tactical element”. While it is possible through skillful play to minimize the house advantage, it is extremely rare that a player has sufficient skill to completely eliminate his inherent long-term disadvantage (the house edge (HE) or house vigorish) in a casino game. Such a skill set would involve years of training, an extraordinary memory and numeracy, and/or acute visual or even aural observation, as in the case of wheel clocking in roulette or other examples of advantage play.

The player’s disadvantage is a result of the casino not paying winning wagers according to the game’s “true odds”, which are the payouts that would be expected considering the odds of a wager either winning or losing. For example, if a game is played by wagering on the number that would result from the roll of one die, true odds would be 5 times the amount wagered since there is a 1 in 6 chance of any single number appearing, assuming that you get the original amount wagered back. However, the casino may only pay 4 times the amount wagered for a winning wager.

The house edge or vigorish is defined as the casino profit expressed as the percentage of the player’s original bet. (In games such as blackjack or Spanish 21, the final bet may be several times the original bet, if the player double and splits.)

In American roulette, there are two “zeroes” (0, 00) and 36 non-zero numbers (18 red and 18 black). This leads to a higher house edge compared to the European roulette. The chances of a player, who bets 1 unit on red, winning is 18/38 and his chances of losing 1 unit is 20/38. The player’s expected value is EV = (18/38 x 1) + (20/38 x -1) = 18/38 – 20/38 = -2/38 = -5.26%. Therefore, the house edge is 5.26%. After 10 spins, betting 1 unit per spin, the average house profit will be 10 x 1 x 5.26% = 0.53 units. Of course, the casino may not win exactly 53 cents of a unit; this figure is the average casino profit from each player if it had millions of players each betting for 10 spins at 1 unit per spin. European and French roulette wheels have only one “zero” and therefore the house advantage (ignoring the en prison rule) is equal to 1/37 = 2.7%.