To calculate the odds of winning a bet in a casino game, you'll need to know the number of possible outcomes that would result in a win and the total number of possible outcomes.

How are betting odds calculated. Betting odds are calculated by the probability of something happening. For example, if the odds are 4-1 this suggests there is a 1 in 5 chance of winning (4+1), or calculated as 1 / (4+1) = 0.2 which means there is a 20% chance of the outcome happening.