Most casino players are unaware of whether the odds work in their favour or not. For some individuals, the notion of betting odds does not even enter the realm of concerns, as they are primarily driven by the will to unwind and have some fun. In such a case, occupying the mind with percentages and probabilities can only chip away at the experience a person wants to achieve.

On the other end of the spectrum resides a group of players who want to maximize their winning chances. Many gamblers would like to determine which wagers are worth pursuing, and understanding the math behind betting odds can help them do just that.

If you count yourself among those who wish to estimate the chance of success before putting their money on the line, you also might want to consider learning more about betting odds. Knowing different types of odds and how to convert them into implied probabilities can very well be the difference between winning a large sum of money and leaving the casino without having a penny to your name.


Learn About the Main Types of Betting Odds

No matter which casino you visit (you can find some reliable ones at, you should learn about the difference between the three main types of betting odds. These are fractional (British) odds, decimal (European) odds, and American (moneyline) odds. The type of odds you will encounter primarily depends on the venue you decide to visit. While some casinos prefer to use fractional odds, others might favour American ones.

Regardless of the odds type, all of them essentially present the same thing — the percentage probability of a specific event. They just do it in different ways. Fortunately, you can convert one type of odds into another. Here is a short description of each of these three types of odds to help you with the process:


  • Fractional Odds — If you live in the UK, you probably have already seen this type of odds. They are usually written as a fraction (e.g., 5/1, 10/1). However, sometimes they are given as the ratio of the profit to the stake, such as three-to-one.
  • Decimal Odds — Decimal odds show how much money you can earn for every $1 you wager. For instance, if you wagered $100 on some event with the decimal odds equal to 3.00, you will win $300 if your bet was correct. This type of odds is popular in multiple countries in Europe, as well as Australia and Canada.
  • American Odds — It should come as no surprise that American odds can be frequently seen in casinos located in the United States of America. This type of odds shows how much money you need to put at stake to win $100 (if accompanied by a minus sign) or how much you can win for every $100 you wager (if accompanied by a plus sign).


Start Converting Odds To Implied Probabilities

Besides converting odds from one type to another, you can also convert them into implied probabilities. This way, you can get a clearer picture of how much you really put at stake with each wager, regardless of how it was initially presented.

To get the implied probability of the outcome, you must divide the stake by the total payout. This process is the most straightforward in the case of decimal odds. In this case, all you have to do is divide one by the odds offered by the bookmaker and multiply the result by 100.

For example, if a bookmaker offers the 5.50 odds for some event, the implied probability for your bet is about 18.2 percent. The higher this number goes, the greater the likelihood of the outcome.


Recognize the House Edge

The final thing you need to understand is that whether you place a winning bet or not — the house always comes out on top. The fact that the team you placed your bet on wins or loses does not matter to the bookmaker that set the odds. Why? Because the odds are not fair.

When you add the implied probabilities for each possible outcome of an event covered by the bookmaker, you will notice that their sum exceeds 100%. However, the sum of all probabilities should always equal 100%. This additional amount over the 100% cap ensures the bookmaker will earn a profit, provided it accepts bets on all outcomes in the right proportion.


The Bottom Line

The knowledge of math behind betting odds will help you make better decisions and avoid costly mistakes. Once you learn about the main types of betting odds, start calculating the implied probabilities before placing your bets, and recognize the house edge, your chances of winning will grow significantly.

When you bet on events where the probability assessed for an outcome is higher than the implied probability estimated by the bookmaker, you will win more regularly than before. However, keep in mind that the payout you will receive will never be enough according to the actual chances you had when you placed the bet, as the odds established by bookmakers are never fair.