Let us assume we are playing the European variation of the game where there are 36 numbered pockets on the wheel plus a single-zero pocket. Naturally, this principle can be applied in the game of roulette as well. Bear in mind the total number of outcomes includes both the ways to win and the possible ways to lose. This way we get the following result: 1 / 2 = 0.50 x 100 = 50%. To convert the probability of tails coming up into a percentage, one needs to divide the first number of the fraction by the second number. In this instance, we are betting that tails will come up so the probability of this happening can be expressed as 1 out of 2, 1 to 2, 1:2 or 1 / 2. There are only two possible outcomes of a coin flip – either heads or tails will come up. Ask yourselves what is the probability of tails coming up the next time you flip the coin. The concept of probability can best be explained by giving the coin-flip as an example. So in this instance, 1 represents the number of ways to win with a straight up bet, while 37 stands for the total number of possible outcomes. For every straight up bet, there are two possible outcomes – the player either wins or loses. In European roulette, all 37 numbers have equal chances of coming up.

The second number or 37 in our example, represents the overall number of possible outcomes. When the probability is expressed as a fraction, the first number stands for the expected frequency of a given event occurring. When the concept of probability is applied to roulette, it is expressed as “1 out of 37”, for example, or is written down as 1/37, which is the same thing. In casino games like roulette, however, the term denotes the likelihood that a given number will come up. Generally speaking, the term “probability” can be defined as the likelihood that a specific event or outcome will occur.

Roulette expected payout of a red bet