American Odds Explained

Key points

  • Odds are displayed with a plus or minus sign. The numbers are often three digits, but they can go to four or more places.
  • This format is referred to as American odds, while decimal and fractional odds are the standard elsewhere.
  • Bettors can determine the favorite or underdog based on the direction or value of the numbers.

Appropriately known as American odds, these are the three-digit numbers that are part of any standard bet listing, such as -110 or +105. Here’s a detailed look at how they work and everything else you need to know.  

What are American sports betting odds?

American odds are three digits (or more) in length, and can have a plus or minus sign in front of the number.

Sportsbook odds indicate the favorite and underdog in a matchup. They also show how much you’ll profit on winning wagers, as well as the overall implied likelihood of outcomes. We’ll explain how to figure that out in a bit. The numbers also help to set expectations.

  • Moneyline: A tight range, such as -125 for the favorite and +105 for the underdog, suggests that the sportsbook still views the underdog as a decent chance to win. A large split, such as -360/+280, indicates more of a mismatch, at least on paper.
  • Spread: The same holds true for the size of the spread. A spread of -2 indicates two relatively evenly matched teams in the eyes of the sportsbook. Spreads of 10-plus points, meanwhile, indicate more of a potential mismatch.
  • Totals: The total line provides a ballpark for the type of game to expect: low- or high-scoring, or somewhere in the middle.

The odds won’t always be exactly on the mark when it comes to the final outcome, but they do help to set expectations on what might be to come. For sports bettors, part of the goal is to learn how to spot the potential values and wager accordingly.

Example of how American odds work

At US sportsbooks, a typical game listing will include the odds for all of the main pregame bets and look like this:

With American odds, there’s a simple rule to remember on spreads and the moneyline: negative numbers indicate favorites, and positive numbers indicate underdogs.

For this example, the Miami Heat are the moneyline favorites and eight-point favorites on the spread.

For spreads and totals, there are two numbers to think about: the line for the bet (eight points on the spread and a total of 208 points) and the odds for each choice, which are -110 across the board for this contest.

How payouts work for American odds

Payouts for winning wagers use the odds from when you bet. While the numbers can shift after you get your wager in, you’ll be locked in at what the odds were at the time of your bet.

When you add your bets to the slip at an online sportsbook and choose your stake, the betting slip will display your potential return. You can also quickly ballpark it by remembering the following:

  • Negative odds: The number is equal to how much you have to bet to get back $100.
    • Odds of -110: Bet $110 to win $100.
  • Positive odds: The number shows how much you’ll get back on a winning $100 bet.
    • Odds of +110: Bet $100 to win $110.

The same ratio applies to other bet amounts, such as betting $11 to win $10 at -110 or wagering $10 to win $11 at +110.

Can you calculate probability from odds?

You can determine the implied probability from sports betting odds. Once again, there are online handicapping calculators that do the work, but you can also do the math yourself.

  • Negative odds (use positive numbers in the calculation): Odds/(Odds+100)*100 = implied probability
    • Odds of -140
    • 140/(140+100)*100 = 58.33%
  • Positive odds: 100/(Odds+100)*100
    • Odds of +120
    • 100/(120+100)*100 = 45.45%

While there are no guarantees that the implied probability will translate into the actual final result, it can certainly help to place things into a better perspective as you research potential wagers.

Understanding line movements

From the initial release of odds right up until the game time, there will often be movement in the numbers. This can be the result of new information, such as a new weather forecast or injury update. The sportsbook can also adjust the odds in response to betting action, usually from respected and known players, or after seeing what other sportsbooks have done.

With odds of -110 on either side, for instance, sportsbooks often would prefer even betting on either option to ensure a profit. Achieving that perfect balance is rarely possible, however.

If there has been a substantial line move in a game that you want to bet on, be sure to review the news to make sure you haven’t missed anything. Afterward, examine the direction of the moves for clues and line shop to compare odds.

Other types of odds

In the US, the American format is the standard, but other markets may use other formats:

  • Decimal: Odds appear as numbers like 1.91 or 2.12. When a bet involves two choices, the lower of the odds numbers indicates the favorite. These odds are generally the primary option in Europe — excluding the UK and Ireland — and other countries around the world.
  • Fractional: This is the standard option in the US for horse racing. Over in Britain and Ireland, this is also the standard listing for sports betting odds. The numbers will appear with a slash or hyphen, such as 5/2 or 3-1.

Converting American odds to other formats

At some sportsbooks, it’s easy to switch back and forth to view the odds in different formats, but it’s not so simple elsewhere. In such situations, you can use an online handicapping calculator, but knowing how to do it yourself is helpful too.

Converting American odds to decimal

Positive American odds: (Odds/100) + 1 = decimal odds

Odds of +120

(120/100) + 1 = 2.2

Negative American odds: 1 – (100/Odds) = decimal odds

Odds of -140

1 – (100/-140) = 1.71

Converting American odds to fractional

Positive American odds: Odds/100 = fractional odds

Odds of +120

120/100 = 1.2 = 12/10 = 6/5

Negative American odds: -100/Odds = fractional odds

Odds of -140

-100/-140 = 0.71 = 7/10 = 3/5

It can get a little tricky with fractions, as you have to convert the decimal and reduce the resulting fraction to how the sportsbook would actually list the bet. The three odds formats may seem to be wildly different at first glance, but actually converting the numbers helps to demonstrate that they’re all tied together.

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