What edge does the casino often have?

People feel like betting even bets (Red, Black, Odd, Even, 1st 18, or 2nd 18) give you a 50% chance of winning. Because most roulette wheels have 0 and 00 on them (38 possibilities) and 0 and 00 are not considered to be Red, Black, Even, Odd, 1st 18, or 2nd 18, you will lose on any spin where 0 or 00 come up. Because of this you have a slightly lower chance of winning an even bet.

The Casino does not pay out based on odds. For example, if you chose 13 and it wins, you will be paid 35 credits even though that bet will only win 1 out of 38 times on average. The casino will pocket the other 3 credits. This brings us to the overall house edge. A casino that has both 0 and 00 on the wheel (as the US does) has a house edge of overall payout of 94.74%.

There are three bets you can make that will pay you even money, or 1-to-1, which means that if you win, you will get back one dollar for every dollar you bet:

Red or black bets, If you put a chip on red then a red number must come up in order for you to win. If the ball lands on a black number, 0 or 00 - you lose. The same thing goes for black - you lose if it comes in red, 0 or 00 and you win if the ball lands on a black number.

1 through 18 and 19 through 36 - If you bet on 1 through 18, then you win if a number from 1 through 18 comes in and you lose if the ball lands on 0, 00 or a number higher than 18. Similarly, if you bet on 19 through 36, you win if one of those numbers comes in and you lose on 0, 00 or any number lower than 19.

Odd or even bets, if you put a chip on odd then the ball must land on an odd number in order for you to win. If it lands on 0, 00, or an even number - you lose. If you bet on even, you win if an even number shows up and lose if the ball lands on 0, 00 or an odd number.