All casino games, regardless of those in the brick and mortar casinos or online casinos, are designed to have the House Edge (also known as House Advantage) built into the game. House edge refers to the mathematical advantage that the casino would have over the player, expressed as a percentage of the player's wager.
Taking the American Roulette as an example, the wheel consists of numbers from 1 - 36, plus 0 and 00. The odds of winning for the player will be 1 in 38 or 37 to 1, meaning a $1 wager on the winning number will make the casino return the original $1 that the player has wagered and payout $37 as winnings. In this scenario, the odds presented will be the true odds. However, in order for the casino to make profits and continue to run their businesses, the casino will only pay 35 to 1 for the above scenario. The player will receive his original $1 and $35 as winnings. The difference between the odds that the casino pays out and the true odds is therefore known as the house edge, or the long term expected winning of the casino. For the American Roulette example above, the difference in winnings is $2, which if taken as a percentage of the true return of $38, is 5.26%. Therefore, 5.26% is the house edge for the American Roulette.
House edge varies for different games and casinos, due to the difference in game rules and odds. However, the method which the house edge is calculated is similar to the above roulette example. To find out the typical house edge for other casino games, please refer to the table below: