How ‘Vegas’ Betting Odds Work
Betting on sports can be quite a daunting prospect for those new or relatively unfamiliar with the process. Check out any online sportsbook and the number of sports, events within those sports and betting markets available within them can appear somewhat overwhelming to those not familiar with sports betting.
Then there are the odds. These can seem unfathomable to the novice bettor, particularly as there are typically different formats in use in different parts of the world, whether in London, UK or in Las Vegas, USA.
Betting Odds Formats
In North America, they typically use ‘American Odds’ or what is also still commonly referred to as “Vegas odds” because historically sports betting odds were always formulated by the Las Vegas bookies since sports betting has been legal in Nevada since 1949.
The most common sports betting market is the match / game winner market which is also known as the ‘Money Line’ (ML). This usually includes any overtime played. Other types of bets exist too – such as futures, parlays, props, and ‘teasers’. For more information on these bet types check out this detailed post on how to bet on sports at Vegas-odds.com
In the UK, which is pretty much the home of gambling as we know it today, odds are usually displayed as ‘Fractional Odds’. In Europe and the wider world, the preference tends to be towards ‘Decimal Odds’.
Below we’ll give a brief explanation of each format, with details of how to convert from one format to another and how you can work out the probability percentage of your bets using the available odds.
American Odds
We’ll start with American odds. Let’s look at a couple of examples of how to bet on sports.
The odds on any sports bets are simply used as an indication of the return you will receive on the amount of money you have staked on a bet.
With American odds, if the odds quoted are positive, the betting odds refer to the amount you would win on a $100 bet. If it is negative, the amount quoted is what you would need to stake to win $100.
So, for example, for example if the odds are quoted as +150, this means that if you bet $100, your return will be $150 (+ your original stake) should your selection win.
With regards to minus/negative American Odds, if you were quoted say -120, in order to win $100 you would have to stake a bet of $120. That is, you would need to stake $120 on the result to make a profit of $100 on a winning bet. Again your original stake is returned if you win.
Convert American Odds to Decimal Odds
In order to convert American odds to decimal odds, if the American odds are positive, simply divide by 100 and add 1. If they are negative, divide 100 by the American odds (without the minus sign) and add 1.
- So, for example, +150 is (150/100) +1 = 1.50 +1 = 2.50.
- With -120, the equation is (100/120) + 1 = 0.83 + 1 = 1.83.
With decimal odds the figure shown simply represents the amount of your total return (including your take) to a 1 unit stake. So a $1 bet at 2.50 would return $2.50.
Convert American Odds to Fractional Odds
Using the same American odds to convert to fractional odds, for +150 we would have (150/100) = 6/4 (this could be written as 3/2, but 6/4 is the way in which these particular fractional odds are generally stated in the UK).
In the case of -120, it would be (100/120) = 5/6.
With fractional odds the first number shown is the amount you would win should you bet the second number. So for example, at 6/4 you would make $6 profit for every $4 you bet. ($10 total return) and with odds of 5/6 you would make $5 profit for every $6 you stake. ($11 total return)
Convert American Odds to Implied Probability
In order to convert American Odds into their implied probability, we make the calculation of 100 divided by the American Odds (if they are positive) +100. So, using the aforementioned odds, we would have 100 / (150 + 100) = 100/250 = 0.40. To convert this implied probability into a percentage, we simply multiply by 100, so that would be 0.40 x 100 = 40.0%.
In the case of negative American Odds, the calculation would be as follows: 120 / (120 + 100) = 120/220 = 0.545 as the implied probability. We then multiply by 100 again to get the percentage, so 0.545 x 100 = 54.45%.
