Odds of Winning and Chances at Roulette
The winning probability is the value, which can be calculated by the aid of probability theory. Percentage values are most meaningful here. A probability of 100 percent means the safe arrival of an event, and a value of 0, the safe lack of an event. The payout ratio describes the relationship between the stake and the payouts. The terms of odds and payout ratio are used synonymously. In roulette the payout ratio increases proportionally with decreasing probability. In other words: the the lower the probability, the higher the payout.
The sheet below explains the roulette rules for different types of bets. The odds for each betting type depends on its probability. The roulette desk usually imposes minimum and maximum bets. Players can continue to place bets as the ball spins around the wheel until the dealer announces no more bets or rien ne va plus.
Payouts  Probability  Bet example  

Straight Bet / Plein / 1 number  1 : 35  1 : 37 = 2.7% 

Cheval / Split bet / 2 numbers  1 : 17  2 : 37 = 5.4% 

Transversale Plein / Street bet / 3 numbers  1 : 11  3 : 37 = 8.1% 

Square bet / Carre / Corner bet / 4 numbers  1 : 8  4 : 37 = 10.8% 

Double Street Transversale Simple / Six Line  6 numbers  1 : 5  6 : 37 = 16.2% 

Dozens, Columns / 12 numbers  1 : 2  12 : 37 = 32.4% 

Simple Chances / Red / Black / Even / Odd / 118 / 1936  1 : 1  18 : 37 = 48.65% 
* All numbers corresponding to a roulette wheel with 37 slots.
Determining the percentage probability of a bet type in roulette is easy:
Probability of 1 Number is: 1: 37 * 100 = 2.7%.
If 2 Numbers are played the winning probability is therefore 2 * 2.7 = 5.4 percent.
Important note on the payouts:
In addition to the payouts, you get back your stake itself.
An example of a Straight with a stake of 1:
payout amount = stake * 35 + stake = 1 * 35 + 1 = 36