Figuring the Odds

Sports odds involve giving gamblers the chance to achieve a profit if they can predict something that will happen during a sporting event (or something that involves sports) or guess the outcome of a sporting event. Gambling on odds can take place at an online casino or at a racetrack, through a land-based sportsbook or at a brick-and-mortar casino betting venue.


“Odds” represent a financial contract between the bookmaker and the gambler. There are three types of odds in sports:

  • American odds
  • Fractional odds
  • Decimal odds

The three types of odds may look different but they actually represent the same thing -- payouts delivered for winning bets. calculated in relation to the amount of money that was wagered.

When sportsbooks, casinos and other bookies pay out a lower amount than what they received in bets, they profit. In addition to the profits that they receive on bettors’ losses, these bookmakers also collect commissions. This is called the “juice” and it ensures that they will make some sort of profit on the bet, one way or another.  

Sports odds tend to be established as set odds. In this way, the bookmaker can expect equal betting on every side of the bet. By setting the odds the bookmaker can be close to absolute certainty that he won’t lose money, regardless of what happens during the sporting event itself.

American Odds

Bookmakers in the United States display sports odds by showing either a minus sign (-) or a plus sign (+), followed by a number. Odds with a plus sign represents the amount of money that would be won if $100 is bet on an underdog — a competitor or a team that is not expected to win. Odds with a minus sign show the amount of  money that must be bet on a favorite — the competitor or team that is expected to win — in order to win $100.

For example, for betting on a favorite, the number -120 would indicate that the bettor must bet $120 USD in order to win $100. +115 would mean that, as odds for betting on an underdog, a winning bet of $100 would earn the player $115.

This type of bet might be used for placing a bet on a sports event in which there’s one underdog and one favorite (such as a basketball game). In such a case,  the number listed for the odds favorite is higher than the number for the underdog's odds. This gives the bookmaker a better chance to make a profit.

Gamblers should be aware that, when using American odds, a winning bet’s total payout is $100 over and above the displayed number. For example, if you win a bet in which you wagered $120 with -120 odds, you would receive a total of $220  — your original bet amount plus your winning $100. If you place a $100 bet on an underdog with +115 odds and you win, you receive back $215 total -- the $115 that you won plus your original $100 bet.

You don’t need to always bet the exact amount that’s shown. You can bet more than $100 or less. For instance, if you placed $3,000 on an underdog with +130 odds and win, you would receive your original $3000 plus $3900 ($130 USD for each $100 bet.)

Fractional Odds

Fractional odds are popular among horse racing fans. They involve odds that are displayed in fractions (i.e. 8/6, 4/1 or 9/1). You’ll hear them spoken as "eight to six," four to one" or "nine to one." The first number refers to the amount of money that can be won on a bet in the amount of the second number.

For example, if you bet at 4/1 odds and win, you receive $4 for every $1 that you bet. If you win a bet at 3/1 odds, you would win $3 for every $1 that you  bet. Payouts include the amount of the original bet which is added to the payout amount. So, if you bet $150 at 3/1 odds, you would receive $600 back from the bookmaker — your original $150 bet plus your $450 winnings.

Decimal Odds

Decimal odds differ from American odds and fractional odds in that they show the bettor exactly what the payout will be based on, including the amount of the bet. In decimal odds the return of the original bet amount is figured into the total win. Decimal odds are expressed in decimals, such as 1.50, 2.50 or 4.50.

For such bets, a winning bet of $200 would result in a total payout of $300, $500 or $850 -- the amount wagered,  multiplied by the decimal shown in the odds. Decimal odds is a popular type of bet option in Europe, Australia and in Canada.

Additional Calculations

Additional calculations include point spreads and over-under bets. These types of wagers aren’t the regular betting odds that most gamblers take on the majority of sporting events but they represent an added element of calculation.

Point Spreads

If you’re betting on a sporting event in which a score is kept, you can bet either on which side will win or on your prediction of the margin of victory. Straight-up bets are those wagers that are placed on the side that you think will win. This is also referred to as betting “on the moneyline”.

A point-spread bet is a bet that’s placed on the margin of victory. Point spreads are indicated in numbers preceded by a plus sign for an underdog or a minus sign for a favorite.   For instance, you might see a - +7.5 for the underdog in a football game and a 7.5 for a favorite in the same game.

There are also bets that you can place on a favorite -- you win a favorites bet either by betting on the underdog, which you win if the underdog wins the game or loses by less than the point spread, or by betting on the favorite which you win when the favorite wins the game by more than the point spread. 

For instance, say you wager on a team at a point spread of +8 -- if the team loses by only six points, you win your bet. On the other hand, if you bet on a team at a point spread of -6 and the team won by only one point, you lose your bet. Typically, bookmakers establish the point spread based on both what odds will bring in equal betting on both sides and the expected result of the game.


Over-Under bets are also referred to as betting on the total. In this type of favorites bet, the bettor wagers on the total number of points that he predicts will be scored in the game. This type of bet doesn’t take into account the number of points scored by either of the teams or relate to which of the teams wins.

For example, if a basketball game’s over-under is 200, a bet on "over" would win if more than 200 total points were scored. A bet on "under" would win if fewer than 200 total points were scored.

Other Types of Bets

The bet types listed above are the most common kinds of wagers. Other types of bets include:

  • Future bets -- bets on results that will take place in the future.
  • Parlay bets -- bets on several different elements in which all of the elements must be correct to win the bet.
  • Props bets -- bets on specific results, such as how many times during a game a specific event will take place or how many points a single player will score.
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