How to read betting odds: Understanding American, fractional, and decimal odds

A sportsbook in Maryland where customers can wager on a variety of events. Photo by Julio Cortez/AP.

Before diving into specific betting strategies, it is best to grasp the basics first. How to understand betting odds is paramount to success.

Sports betting can be intimidating at first glance. Lots of bells and whistles, hundreds of games to choose from, as well as fractions and decimal points. But have no fear, the symbols you see in a sportsbook are closer to linguistics than math as this is just the language of sports betting.

How to understand betting odds

When joining a sportsbook, you’ll have an option on how you want your odds to be displayed: American, fractional, or decimal. Choosing your display settings has zero impact on the actual odds — it is for personal preference only.

In this piece, we’ll break down the three ways that odds are displayed: American, fractional, and decimal.

How are odds set?

There are odds for everything. Want to wager on the NFL? There will be odds for that. The same goes for everything from the NHL to F1 — just about any sport you imagine will have accompanying odds.

Regardless of the sport, the bookmakers are placing an implied probability on what will occur based on a massive number of internal and external variables. Sportsbooks consider what will occur in the game to set the opening line. When a certain amount of money gets wagered on an event, these odds can move based on how the sportsbook wants to hedge the action on any event.

The way these odds are displayed are just different ways to read what the operators believe will occur.

American odds

American odds are the most popular in Canada and are often what you will see displayed on social media and advertisements here.

The first thing you need to know about American odds is what the plus and minus signs mean. If you see a bet with a (+) before it, that means the selection is “plus money,” and the return on your bet will equal or surpass your stake placed. If there is a (-) sign before the bet, you are wagering on something with an above 50% implied probability of occurring, and therefore your return will be lower than your stake.

A team or player with a minus sign before its moneyline odds or point spread represents the favourite. You will know who the underdog is based on the plus sign.

American odds are set on a $100 baseline. The larger the number after a (-) sign, the higher the implied probability and the bigger the favourite. Conversely, the larger the number after a (+) sign, the longer the odds are, and the higher the return.

American OddsStakeProfitImplied probability
-300$300$10075%
-150$150$10060%
+100$100$10050%
+200$100$20033.33%
+1000$100$10009.09%

If you’re betting on a -1000 favourite, sportsbooks are placing a 90.9% probability that team will win. Therefore, you will need to bet $1000 to win $100. If you’re betting on a +235 underdog, a $100 bet will net you a $235 profit. The extra money reflects the sportsbooks belief that the underdog will probably lose.

Fractional odds

Fractional odds are more commonly seen in European sportsbooks and are often associated with sports like horseracing. They might look complicated, but in reality, they’re quite simple. Fractional odds are just the ratio of the amount won to the staked placed.

For example, a 5/2 fractional odds means you would have a return of $5 off a $2 bet for a $3 profit. If you wanted to up the stakes, you would profit $250 on a $100 wager. Five is 2.5x more than two, therefore it would equate to +250 American odds (28.57% implied probability).

Using the same odds in the table above, let’s see how fractional odds would look.

Fractional OddsAmericanStakeProfitImplied probability
1/3-300$300$10075%
2/3-150$150$10060%
1/1+100$100$10050%
2/1+200$100$20033.33%
10/1+1000$100$10009.09%

Now that we've covered off the first two, we'll turn our attention to decimal odds.

Decimal odds

Decimal odds aren't as commonly used, but some people find it to be the most comprehensive.

It simply represents the amount won per $1 wagered on any event. Therefore, odds of 2.30 would mean a $1 bet returns $2.30, for a profit of $1.30.

Furthermore, a $100 bet returns $230, for a profit of $130.  

DecimalFractionalAmericanStakeProfitImplied probability
1.331/3-300$300$10075%
1.662/3-150$150$10060%
2.001/1+100$100$10050%
3.002/1+200$100$20028.57%
11.0010/1+1000$100$10009.09%

If you’re still a bit confused on how to understand decimal betting odds, think of it as a math formula:  

Total payout = stake x decimal odd number
$300 = $100 x 3.0
$133 = $100 x 1.333
$723 = $100 x 7.23

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