guide to sports betting odds

Guide to Sports Betting Odds

Understanding how sports betting odds is an obvious first step to becoming a successful bettor. Odds can vary from book to book and can shift in seconds, particularly when betting on live games.

There are three types of odds bettors need to understand prior to placing a bet. These include American odds, decimal odds, and fractional odds. 

As a US sports bettor, you will typically deal with American odds. These are what you will find when betting on NFL, NBA, NHL, MLB, and college football and basketball.  That being said, decimal odds are easier to read and convert into probability, and most books will allow you to switch to decimal odds right from the website or app.

Fractional odds are much less common and most bettors only use them when betting on golf and horses.

Let's take a closer look at how each type of betting odds works.

How American Odds Work

American odds are the default odds shown on most US sportsbooks. Once you are used to reading these odds, you will inherently know exactly what the odds/probability is without having to break out a calculator. That being said, you will likely want one for this lesson, let's jump into how you calculate probability and payouts using American odds.
betting odds explained - american odds

Calculating Probability with American Odds

American odds are the default odds shown on most US sportsbooks. Once you are used to reading these odds, you will inherently know exactly what the odds/probability is without having to break out a calculator. That being said, you will likely want one for this lesson, let's jump into how you calculate probability and payouts using American odds.
calculating payout using american odds

Calculating Payouts with American Odds

American odds are the default odds shown on most US sportsbooks. Once you are used to reading these odds, you will inherently know exactly what the odds/probability is without having to break out a calculator. That being said, you will likely want one for this lesson, let's jump into how you calculate probability and payouts using American odds.

How Decimal Odds Work

The good news is the tough part is over. It is important to understand how American odds work for several reasonss. While you can choose to display odds as decimal odds on your sportsbook's website or app, often times odds are displayed as American odds when discussed, written about, or displayed inside of brick-and-mortar sportsbook locations.

That being said, decimal odds are a much simpler system, and are by far the most popular odds system on a global level. Let's take a look at how decimal odds work and how you can calculate probability and payouts using decimal odds.
calculating probability with decimal odds

Calculating Probability with Decimal Odds

As you can see in the graphic calculating probability with decimal odds is considerably easier than calculating probability with American odds. The formula is extremely straight forward, and does not need to be adjusted for what is considered negative odds in the American odds format.

Simply divide one by the decimal odds for that given bet. The closer odds get to 1, the higher the probability the bet will pay out. A heavy favorite may have odds of only 1.05 which would of course indicate a 95.23% win probability.
payout with decimal odds

Calculating Payouts with Decimal Odds

Calculating payouts with decimal odds is considerably easier as well. Simply multiply your bet amount by the decimal odds, then subtract the bet amount out of the total payout to calculate your winnings. 

As you can see in the example, a $10 bet with 2.3 odds would pay out a total of $23. When you subtract out your bet ($10), you are left with $13 in total winnings. Assuming you are betting even dollar amounts like $10, $20, $100... you should be able to calculate winnings in your head when placing bets.

How Fractional Odds Work

As we mentioned in the open, fractional odds are the least often used form of betting odds. Where you typically see this format is where you have a field of players, teams, or horses. Obviously this means you find fractional odds when betting on team futures like Super Bowl odds, player futures like MVP odds, PGA tournaments, and horse races.

While fractional odds look different, calculating probability and payout with them is a fairly straight-forward process. Here is exactly how you use fractional odds.
probability with fractional odds

Calculating Probability with Fractional Odds

To calculate probability with fractional odds you simply need to memorize the quick formula shown on the left side of the graphic above. The formula for fractional odds probability is denominator divided by denominator plus numerator. So, given odds of 9/2, the formula would give you a probability of 2 divided by 9 plus 2, or or 2/11. Solving will give you a probability of 18.18%.

Again, you will find this format anytime you have a field of potential winners. If you think a boxer has a 75% chance of winning, but an odds probability of 60%, that would be a great bet to make.
calculating payout with fractional betting odds

Calculating Payouts with Fractional Odds

Calculating payouts with fractional odds is just about as easy as calculating payouts using decimal odds. Simply multiply your bet by the fractional odds. In the case of the given example, a $10 bet with 9/2 odds, would pay out $45 - ($10 x (9/2)).

Because these odds are used in events with a field, you will often find big payouts in events that feature fractional odds. Again, the most common bets you will make with fractional odds are futures like preseason Super Bowl odds, PGA bets (golfer vs the field), and horse racing bets.

Betting Odds Summary

Understanding how these three betting odds formats work is essential to becoming a profitable in sports betting. While all the numbers you see across sportsbooks may seem intimidating at first, with practice you will get really fast at calculating probabilities and payouts.

Bookmark this page and reference back to it as needed as you get started in sports betting. Even better yet, subscribe to our newsletter to get a weekly email that breaks down odds, probabilities and payouts for you!
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